The first thing I would suggest is, that if you live in a country where mental health issues are taken seriously, consider talking to your doctor. It may be that you have an anxiety disorder or depression or both.

I have an anxiety disorder for which I take medication and received counseling. My condition is life-long and chronic but with medication it is bearable. Going for help was one of the best things I ever did.

I also think it is important to remember that you are not alone. Lots of people have difficulties when transitioning to University. It is an incredibly stressful time of life, so many new experiences and pressures all at a time when you are likely to be going through lots of emotional changes related to growing up. It is natural to go through this and most people do at sometime or another in the early twenties. You just got there early! I imagine that if you could reach out into the heads of the other people around you at Uni you would find many of them feel the same way you do, to some degree or another.

Please understand that I am NOT a doctor so when I say this it is without any expert knowledge. What you have described sounds to me a bit like ‘imposter syndrome’. You can find out more about this on Wikipedia.

http://en.wikipedia.org/wiki/Impostor_syndrome

I really hope you find some peace.