I think I am going crazy..what should I do?

It seems like your a really nice guy and I'm sorry about how miserable you seem to be. As for question one yes you should. But people don't just "move on" it's not that easy. Yes you will think about her constantly I do about he guy I like. But it will p. You will end up getting occupied with something else even though it doesn't seem possible now. You will find new interests not in girls maybe as you said but hobbies. Regret? Of course people go through this all the time. Your case isn't too unique. Good luck man