What’s wrong with me😭

My boyfriend and I have been trying to conceive for about 6 or 7 months now and no luck. I’m starting to think I’m infertile? My periods have been really irregular. I had my period for three months nonstop and went to the doctor and they put me on birth control. When I went off, my period has been coming every other week. Every time I think this is it. This is the time I get pregnant. My period shows up. I’m trying not to give up hope and not to be stressed out about it but it’s hard. I’ve also gained about 20 lbs in a short amount of time. Could this also be a factor of infertility? I’m trying to eat healthier, drink more water and exercise to lose weight. Maybe that will help? Has anyone had a similar experience? What should I do? Also I am 20