My mom doesn't believe me that I think I have OCD. What do I do?

It is hard to give you a good advice how to make your mother believe you. I think your disorder (neurosis) is conditioned by pubertal period you are in. Try to masturbate, it'll make you condition somewhat easier. Make complaints about bad sleep in order to make your mother to draw your to a psychiatrist. Sleep disorder is not such scary for your mom than OCD so it is more probable to make her visit the doctor with you.