Why am I this way? How do I fix it?

Right now my mental state is quite unstable. I pretty much do not enjoy any thing these days. I typically hate failure. If I fail at something the first time I try it, I don't do it again. I've been talking to a counselor and we found out I define myself by how others see me and not how I see myself. I typically don't do things just for myself, and if I do, I feel it's a form of weakness. I've been able to get this far in life, and I have competitive grades, but now I'm getting to the point where I can't just get by without actually learning and understanding. I want to be different, but I am not motivated to succeed because I can't find reason to. I've always felt that I'm a worthless person, and many people throughout my past have reinforced it. Right now I feel I a worthless and weak person. I am not motivated in school. I am currently somehow a junior in engineering, and I really don't know if I am going to make it. I've considered changing majors, but because my major is quite hard, I would feel like I'm failing and being weak by switching. I'm sure plenty of people may go through this, but unfortunately it doesn't make me feel better. It seems as though I am incapable of caring. I don't understand why I am this way, and how to be "fixed."