I too once experienced nightmare in english but now I'm extremly proud and active speaker .The things worked for me and I can not hesitate  in sharing my experience with you .

4 things you need to keep in mind :-

1.Confidence is must -If you dont have , try to build by speaking on any topic by recording your voice and improve it in every possible way .The other thing i can must tell you speak to yourself like Your mirror image

2.Think in english .

3.Watch english movies , read english novels and newspapers.

After this now find out some grammatical errors and correct it .

I hope you will get what I want to say.

Hey Sandeep

Firstly, It Is Not A Weekness. Fluency In English Comes From Day To Day Practice. For That You  Can Read Newspapers , Read Good English Books , Read Articles . Make A Habit Of Reading Daily. You Can Also Read And Stand InFront Of Mirror,To See How you are representing Yourself. But , First , You have To be Confident Enough. Being Confident Enhances Your Way Of Speaking And Will Definitely Work For You To Represent Yourself In A Correct And Proper Way.

I Hope It Helps

Good Luck