Trying to have a baby!

My fiancé and I have been together for 7 years and have been trying and trying to conceive and NOTHING. We have actively been trying this year. Yes, we tried before, but nothing major just a few times and got over it. The problem is that I am extremely irregular with my menses and sometimes do not even get a period. Sometimes I would go a month with it almost 2 (yes every single day) and sometimes I would not get it for a whole year! I went to my GYN and she prescribed Prometrium to get back on a regular cycle. I have to take 1 pill everyday for 12 days, every month. I've been on it for 3 months and it has given me my period for those 12 days with normal bleeding. However, no baby yet. I know this pill is not supposed to get you pregnant, but having unprotected sex and not getting results after months and months of trying, I am just worried and believe it or not, stressed and frustrated! HELP!!!! Any advice???