Disappointed with a question

Hello.....so I've only been trying to get pregnant for about 5 or 6 months now and nothing. I am in my 30s which I know can make it a little harder to conceive but I get very sad when I get my period. I'm not quite sure if it is just how the cookie crumbles, it's me or my bf. I did have a baby 16 years ago but not sure if it could be me or my love. So my question is who do we go to in order to find out if maybe it's my bf's sperm......not sure what kind of doctor does that? Please help I am so wanting to have another baby. Thank you!!!