For anything you do in life, a clear goal /vision, adequate motivation / enthusiasm, hard work / discipline and the ability to take risks/ challenges are critical attributes. Your are very lucky that you have identified your problem and you are proactively seeking a solution to it.
What you also require are the key attributes called 'discipline' and 'enthusiasm' with which you can achieve anything you want.
Your enthusiasm is the reason you wrote in at Citehr. The next test is to be disciplined and follow the suggestions given here.
1. My first suggestion is to read as much as possible in English ALOUD. A standard daily English Newspaper and the Readers Digest have very good reading material. If possible record your voice and listen to it to know the areas the sounds, words and alphabets that give you trouble and on which you need to work.
2. The mother tongue influence is a problem for many considering that very few of us are native English speakers. To reduce that make more English speaking friends and make a determined effort to speak only in English, even if you keep forgetting words, or tend to stammer or your friends tend to laugh at you. This will require a lot of will power but believe me you will soon improve. If someone corrects your pronunciation don’t take offence, instead be grateful that he/ she is helping you correct yourself.
3. I would also suggest you try to learn at least 3 -5 new words and look up the meaning in a dictionary. then try and use these words in your daily work and in your communication to improve your vocabulary. Find synonyms for words that give you trouble and use the synonym.
4. If you still feel that professional help is needed then you will have to attend English speaking classes
5. Finally, if you can, do visit my blogs listed below regularly and try to learn the new words in it and also be inspired by it.