TTC Advice???

Me and my guy have been together 4 years got together in September and found out I was 4 weeks and 3 days, miscarried at 5 weeks, and have been TTC every since. STILL NO LUCK. I get discouraged at times because I feel as though I can't have any kids everyone around me gets pregnant so fast and easily. I'm unsure when I'm actually ovulating I don't believe I even ovulate, with fertility treatments being so expensive it's like it's almost impossible to get pregnant I know it's something wrong because my stomache aches sometimes after sex like cramps. ...any advice of what may be going on? Or does anyone else have this problem?