What is wrong with me

baby girl
I had took the depo shot after I had my first son and now it's is 2 years off depo I have my period every 37 days and still haven't became preguant and I have sex everyday make sure ant missing the right time it's been  3 months trying  and nothing I just to give up and maybe happen on its own time but I feel bad becouse with my first I didn't even try it just happen and I was only 15 and now that I'm 20 and I'm marry and have a house and it just look like it don't want to happen..please help