Welcome rahulr,
Having a programming experience in C and C++ will go a long way towards understanding what's happening in the background. Like Don already indicated, Networking knowledge is also key.
Pen Testing can definitely be a sexy and exciting career path. However, it will have it's boring and monotonous parts just like any job. You will have to deal with office politics, just like anything else. Another interesting area is Research, involving your coding background.
You really have to try your hands at a bunch of different things until you find the one you love. I suppose it's a bit like dating

College is the perfect place for both.