Frustrated and afraid

I've been TTC off and on for years. After being told at one point several years ago that the hope of children was fruitless, I brokenheartedly stopped trying and accepted failure. It cost me a relationship and I have not TTC since. Recently a new doctor and round of tests I couldn't afford said "I shouldn't have any trouble conceiving." I also discovered my ex was responsible for my reproductive problems while we were together. He was literally drugging me to avoid pregnancy. It's something I'm still struggling to cope with. So, being told I could in-fact have children I sat and considered my options. I have clung to the knowledge that I was told having children would never happen. The words "post menopausal hormone level" ringing in my head like a punch in the guts. I have mourned that knowledge for years.  I decided to have faith, to believe maybe I had recovered. I chose to let my heart become open to the possibility of children again. I chose to start trying for the child I always dreamt I would have. This time has been an adventure. My partner is fixed and chooses not to pass along genetic traits like diabetes. So we chose a healthy donor who is willing to help us conceive naturally. I've had regular cycles for three years. Some heavy periods and painful menstruation but still "regular" periods. I started TTC this time in September, after a few months of ovulation testing to confirm if any efforts would possibly be fruitful. I was ovulating regularly. My partner and I believe I was pregnant but miscarried in November. December and January both failed to produce a PPT. I was late by two weeks in Feb. but no baby. After giving up TTC for march due to bad timing, I hadn't had a period until today. The frustration has really set in. I've been regular all his time and now, when I believe that maybe I can try again I'm suddenly back to irregular cycles. I don't understand it. I haven't changed my diet or environment. The only change is that I'm now getting "live" semen introduced into my body, where before I wasn't. Is there anyone out there who's having trouble like this or is just feeling downright frustrated? I'm not sure how to keep the thought that perhaps I really can't bear children from taking over. I don't want to experience that heartbreak again. My partner says keep trying, so do my friends. How do I continue when I can't count on my body to cooperate?