How do I stop the habit of getting obsessive with girls and staring at them?

Each person and situation is different so I don't know what answer will work for you but I would take this oppurtunity to get more work done. Keep your mind busy by focusing on your studies and working harder on school. It sounds like you're depressed and feel disengaged from the world and I know how you feel. You feel different than most people out there that are naturally social. This may not be of much use to you but try getting an xbox or something and play online. That might help you communicate with better better cause it's easier to improve on your social skills when you aren't talking face to face with people. It's sounds weird but give it a shot dude. Good luck...