Infertility

For a very long time now I have believed that I cannot have children. Over the years I have had unprotected sex with my partner during everyday pretty much except my period. I am only 21 and I dont want children right now but after about a year of unprotected sex we just assumed I cant have children. I would like to confirm but I actually dont know what doctor I need to see and what I schedule the appointment for. I never had a mom so I dont know who to ask.

Thank you.