I am scared of developing a mental disorder :(?

We are pretty much on the same boat. Anxiety and OCD are related, however not all mental disorders are. I have never heard of schizophrenia being related to anxiety. Try seeing a therapist, mine has helped me quite a lot. There is really no known reason for anxiety, but often stress can trigger it. It also might help to know that anxiety often occurs in teens but does not stay throughout adulthood. In other words, it could be just a phase. I know that what you are going through it really tough, I am going through the same thing. I hope I've helped!