Second guessing.

I've always had irregular periods, and many times its lead to me thinking I could be pregnant and a few days later I finally start. Well I've been thinking for a while that I may be infertile. I was on the Depo shot for about 4 years total. There were times I stopped and took the pill too balance back out but the shot was just more convinent for me at that age so I went back to it. Well I've been off for about 2.5 years. At least around there, and my fiancée and I have been trying to convince for 1.5-2 years now and nothing has happened. Well here lately I've been feeling very strange and have been having strange stomach pains/feelings. Almost like "butterflies". At least that's the only way I can put it. Anyone have any idea of what it could be? Or any ideas that may help me concieve. Preferably natural ways. I don't want to resort to any type of medicine yet.