First tell your parents or guardian you suspect something may be affecting you.
Suggest going to the doctor and to give him/her a call.
If the doctor refers you to someone, call them.
Make the appointments with either of the two.
I was evaluated by a counselor and she asked me questions about my childhood. Particularly my social and academic skills. She asked me about my interests as a child and now. She asked me about my inability to read people very well and many things common to Aspies. She then gave me a test, mine was called the CEP-R (I think) test which evaluated how well I did socializing, reading others behavior and emotions etc.
She talked to me and then brought out the DSM and I matched most of the criteria for Asperger’s Syndrome and she diagnosed me.