Every time I think this might be it...disappointed!

My husband and I have been trying naturally for FOUR YEARS. I haven't wanted to give in and go to a specialist yet, but that's around the corner. I've never been pregnant, not even by accident. I'm starting to think God or the universe or whatever force bigger than us doesn't want us to have kids. It's very upsetting. Most of the time, my cycles are about 31 days. If they're that long, I know it's my normal. I'll go along for months with normal cycles, thinking I've figured out the fertile time. We do it during that time and I think, "yes, this really could be it!" That's when my period doesn't come on time, even though I've had cramping. I take a test, BFN. I wait. Still no period. Cramps are gone. It's 14 days late and I finally get my freakin' period and I'm depressed. My cycle decided to go haywire and obviously we didn't do it at the right time. Meanwhile, more friends are getting pregnant, having babies, and even friends' teenage kids are getting pregnant. Ill-equipped, unprepared teenagers are having babies, so I feel like cruel jokes are being played on me.