Hii Anand!
The only solution to this problem is you speak it more and more. Don't worry and don't feel low. It is a common problem. Not able to speak in English doesn't lower your IQ. Try talking in English without feeling shy, because, you are learning. To increase your vocabulary, read out newspapers, books, out loud. This in turn improves your pronounciation. Speak it more and more and you will be good. Practise is the only key to improve.
Hope you understand.
Good luck!