Starting to lose hope...

My S.O and I have been trying to conceive for over a year now with no luck whatsoever. I'm starting to think I can't get pregnant. I know its not him, because he has a 3 yr old from a previous relationship and I have never been pregnant. I have a doctor's appt in a few weeks that I've scheduled specifically to discuss my difficulties with getting pregnant which scares me that I even have to make this appt. I've always had very regular periods, I've never missed a single cycle since I started my period in 5th grade. Nobody in my family has had problems conceiving so I never would of thought that I would. I think about it all the time and I'm devastated at just the thought that I can't have children. We always have sex when I'm ovulating and I'm honestly starting to think I just can't get pregnant and that somethings wrong with me. I wonder if I even ovulate at all. Sorry this is so long but I just need some advice. I'm really starting to lose all hope and just give up. Thank you ..