Any ladies out there who's men felt they were not fertile and were able to conceive?

My DH is convinced he's sterile or close to it anyway. We've been trying to conceive for a short time now, but I've never had an issue getting pregnant in the past. My first pregnancy was 4 months after my first period(at 17) while I was on BC. My second pregnancy happened after having sex once, with my now ex husband, the week I removed my Mirena. My third, also with my now ex husband, we only tried once as well. With my previous history I am starting to worry that my DH might have the issues he feels he has. I have only just started tracking my ovulation and everything else that goes along with TTC as I've never had to worry about it before. Did you girls do anything to help with your man's fertility before knowing for sure whether or not there was a real issue? I just need advice on what to do next.