39 and ttc #3....

Kelly
My boyfriend and I are ttc. He doesn't have any children of his own. I have a 10 and 12 yr old. My boyfriend is 25 and insulin dependant with type 1 diabetes. We have been trying now for 6 months or so. Having sex daily sometimes more. He ejaculates at minimum 3 time every time. The only time we dont is during AF's visits. Are we doing something wrong? I dont test ovulation, or bpi nothing. I figure we are good considering how much we do it. Now i have had a few months where I would have what seemed like implantation bleeding and not get a "normal" period. I would be sick, sore breasts, fatigue, all the symptoms. I would then take a test and it was a Bfn. The next month AF comes. Any advice?