Hello,

You are eligible but there are different exams for it. it may not be in India but you can do it aboard. There are some criteria  for it. you have to satisfy it.

In India you can go for Mtech only in the domain in which you did your graduation. Mtech is specialisation of btech.

If you want to do specialisation in other domain then you have to go for aboard.

If you are weak in mathematics then you have to work very hard as specialisation needs evolution and solving of hard problems which have no prior solution or method.

Hope it helps!