I honestly believe that it happens when your least expecting it. I have been pregnant 3 times, the first time was a total shock, the second I was trying and it took like 7 months and the 3rd time I had just gotten off birth control so I was going to wait a few cycles before I started trying but surprise I got pregnant the first month.
Even on here you see so many women charting and temping like crazy and it takes forever for them to conceive and yet you get girl's that aren't trying and don't even want to be pregnant that get pregnant so easily. It really isn't fair