Beyond frustrated...

How is it that we bd a million times last month yet nothing is happening. I have taken four tests all bfn. Af is due 4/7. I just I am so frustrated, I got pregnant in three months of stopping my birth control the first time got our bfp and made it to week 6 and had a miscarriage in December had the d&c and was told that would help make everything super fertile and that probably the next time we bd I would be so pregnant! Well let me tell u that hasn't happened. We waited one cycle because after the d&c af was all over the place now I am fully regular again and nothing! I don't get it I am getting so discouraged and my hubby is beyond himself he feels it's him I feel it me. We both have been to the dr before ttc and everything is great not a problem they say. Idk it is really stressing me out I am just so tired of it all. I didn't think I could get any lower than when I had the mc but I am defiantly lower with nothing happening. Ugh do you ladies have any suggestions we do everything that's possible we are both on vitiams and I am taking folic acid 800mg like my dr said. We bd on all fertile days and two days before and after. I just idk maybe it me but I feel we should have a baby with all of that. I don't use the opks because I know I am defiantly in sync with the app. My periods are very regular as well. I don't bbt either is that something I should do? Does that help at all? Help......suggestions....anything!!?!!