Over thinking

So I work for a infertility specialist and everyday I hear and see many many females with different fertility problems. I've been working here for about 4 years and I never thought about my fertility much since I already have two sons 11 and 7. I just got married and we are just going to start trying to get pregnant. Now, I'm thinking like "what if I can't get pregnant? It's been 8 years"!!!  I guess I'm just over thinking it and I shouldn't cause it can interfere with my trying to conceive. I just can't help it. :(