Miscarriage

I had a natural miscarriage Monday, Sept 3rd. The baby stopped developing at 10 weeks. Today, I should be 13 weeks, 3 days. It was my first pregnancy. Going back to the doc, Sept 4th, everything was clear and had passed. No D/C needed. Every Saturday starts a new week and I am free EVERY Saturday and Sunday. I cried and cried some more, along with my fiance, and now I'm feeling better. But I am lost. I question what happened and why it happened. The doctor would only talk about my sugars and how I needed to take care of that b4 trying again. B4 I got pregnant, my sugars were up to 300-490. I had been working on getting them lower but I had no insurance and no doctor. When finding out I was pregnant, I completely changed everything. Mu sugars stayed where they were suppose to.. Fasting 95 or below and 120 or below 2 hrs after eating. I checked regularly 4 times a day EVERY day. Watched what I ate, drank NOTHING but WATER. Didn't even add any additives to make the water taste better. And I can tell you this, I love mtn dew and dr pepper. But I completely cut it out of my life. I did everything I could to take care of myself and make sure baby was ok. I feel like I failed as q mother-to-be. One minute the doctor is telling me my blood type is negative(which I already knew) and that I will be given an RH Shot for future pregnancies and that negative blood will develope antibodies and kill foreign substances (such as a positive blood type baby). Then I was told constantly to work my sugar down b4 trying. 2 factors that could have taken away the baby we so badly wanted. I know doctors don't know what causes miscarriages.. If that was so, they could prevent them from happening all together.. But idk.. I feel like I'm to blame. Am I? Is there something I should/could have done differently?? Any moms with diabetes or negative blood type here with some advice? Family and friends all tell me the same, it's not my fault. But I can't help but blame myself. It was my baby, inside my uterus. And it was my body that killed and aborted my baby.