I don´t like you drive car to Pattaya when you are stressed. Its to dangerous to drive car when you are stressed. I care you. It´s better you fly to bkk and then go by bus to Pattaya. First you must tell your sister you visit her. Maybe she say Don´t visit me.
You can´t be angry her maybe she not listen to you. Try to call her now and tell her about contraception