Trying to become pregnant...

Okay, so my fiancé and I are trying to get pregnant for many many reasons. It's been about 2- 3 months since I've been completely off the pill and I still haven't had any signs of pregnancy or implantation. I've taken 2 pregnancy test and they have both come back negative.. we don't use any protection, lubricant or anything at all. I've been told to lay on my back afterwards.. why aren't we pregnant yet? What could we do? I'm suppose to start my period in a few days so I'm praying about it..

Also, when is the best time to take a test? I've been told 4 days before I'm suppose to start and I've been told not to until after the first day I'm suppose to start.. any comments would help!