scared that I'm not able to have kids

I have been with my Fiancé for 4 years and some months now. We have been engaged for a year. For 3 years we have never used condoms. I have not gotten pregnant. I am scared to really go to the doctor and they tell me I can't have my own child. I mean I do plan on adoption in my future even if I do have my own child but is it likely that I really can't get pregnant? That's all I have wanted my whole life is to start my own family. Does anyone know how much it would cost to get checked about that. I mean I have state insurance but I don't know I think I am more scared to know the answer than anything. I think it will just honestly break me.