WARNING! Male pregnancy, pregnancy inflation, alien impregnation, and birth. Don't like, don't read.
Nineteen-year-old Jake woke up in a room that was definitely not his. He got up and searched for a way out, but the only door would not open. He gave a frustrated huff and sat on the bed to wait. An hour later, a humanoid creature of about seven feet tall with sharp claws on his big hands entered the room. The humanoid alien was suited in armor, and his face was relatively resembled a human male's except its skin was gray with the texture similar to a snake's smooth skin. Jake backed up to the far wall and tried to get as far away from the creature as he possibly could, but the creature took long strides and reached him in three steps. The alien took out a syringe and injected Jake with a drug that put him to sleep.
When Jake woke up next, he was lying in the same room he woke up in. He tried to sit up but he felt a sharp pain in his abdomen. He looked down to see if he was injured, and found a bandage wrapped around him. The door opened, and the alien appeared in the doorway. Jake wanted to get away but his sore middle prevented him from moving. The alien stood by the bed and placed a hand on Jake's shoulder and made him lay back on the bed.
"You have been impregnated with my species' young, and you will gestate them for three months before you give birth. All your needs will be taken care of." With that, it left the room with Jake staring after him.
This couldn't be happening. Men couldn't get pregnant! And why was he chosen by this alien species? There wasn't anything different about him that made him stand out. Jake was shorter than most guys, and he had reddish-brown hair and pale skin. Not exactly unique. But here he was, forced to carry alien offspring for three months.
Jake found out that he was on an alien spaceship that was orbiting Earth. The ship was hidden from human eyes, and therefore not at risk of detection. He had full access to the decks and was able to tell that these creatures had very advanced technology. Teleportation was a reality instead of fantasy, and there was a machine that created his favorite foods in front of his very eyes. Jake also found out that the alien race was dying due to widespread infertility that hit the bearers of children. As far as he could tell, there was no male or female distinction, but only those that could bear children and those that couldn't. The aliens had experimented on other creatures to save their race with very poor results, and wondered if humans were capable. Jake was to be their guinea pig, and the aliens altered his organs so that he would be able to carry and give birth.
Jake had been pregnant for two weeks, and he was constantly hungry. He would eat and eat and eat, but he was still not full. He had a full term pregnant belly now, and it was getting very difficult for him to walk throughout the ship without stopping to catch his breath. Pretty soon he wouldn't have the endurance or strength to walk and he would be confined to his bed. His belly was large and heavy and his skin was taut. His belly button popped out and rubbed against his shirt when he walked, or rather waddled. Jake would place his hands on his belly and marvel at how his body was changing. His hips widened to support his heavy belly, and his rear had become rounder and plumper. Jake didn't know what was in store for him, but if he was already this big at two weeks, he was going to be gigantic at the end.
After the first month passed, Jake was strictly bedridden. His belly grew and grew every day, but he couldn't feel any movement within. His belly was now the size of a full term belly filled with twins, and his belly button was now flat against the round sphere. The skin was pulled tight over his womb. Even though Jake felt so full and heavy with children, his appetite was still never ending. At the end of the day, Jake felt like his belly would burst open because the pressure inside was overwhelming.
Sometimes the alien Jake saw on the first day would come to visit him. The alien would place its big clawed hand on the pregnant swell and stroke it gently, almost lovingly. Jake didn't know what to make of the alien. The creature never mistreated him or hurt him, but Jake was here against his will and forcibly pregnant with an unknown number of offspring.
The second month became very trying for Jake. His belly now looked to be full term with five healthy human babies. Jake was getting desperate. The pressure in his belly was monumental, and it weighed over a hundred pounds. Jake wasn't able to walk if he tried. He wanted this horrible pregnancy to be over with. Jake stroked the expansive sides of his great belly to try to calm himself down, but it only reminded him of how huge his belly truly was. Red angry stretch marks covered Jake's tight belly, and the skin was constantly itchy due it being stretched tight. He continued to eat constantly thanks to some of the aliens that made sure he ate enough. The main alien still came by, but Jake had started to fear it. The seven-foot tall creature would lazily drag its sharp claws over the tightly-filled orb, and Jake feared a sharp claw would pierce through his tight skin and pop his overtaxed belly. Jake released frightful whimpers that only seemed to amuse the alien. If only Jake wasn't so helpless so that he could protect his vulnerable body.
When Jake became three months pregnant, he received more visitors than ever before. They would crowd his room and take turns rubbing and patting the fertile belly. The aliens seemed happy as they spoke excitedly in their language. The month wore on and Jake's belly continued to grow as Jake continued to eat large quantities of food to nourish whatever was within. Jake could only groan in pain and open his mouth to allow food to get in. He stopped touching his belly because each touch only added to his discomfort. He dreaded having the enthusiastic aliens fawn over his belly. Because his belly was so tight and filled to the brim, Jake feared he would burst if he breathed wrong.
One day, the main alien came in to examine Jake. It approached the eight-foot-in-diameter belly and stroked it. Jake whimpered as the sharp point of its claws scraped against the thin, taut skin.
"You are definitely bigger than what we have imagined," the alien said.
Jake did not like the sound of that. "What do you mean?" Jake managed to say between his moans of pain.
"We implanted a great number of young inside you with the idea that several would be unviable and be destroyed by the amniotic fluid. However, it seems every egg we implanted you with is viable. We are most pleased with this development. You have proven to be the perfect bearer." The alien left Jake to curse his rotten luck. Not only was Jake heavily pregnant with alien spawn, but apparently his body provided the perfect conditions for growing that alien spawn.