Not sure what's going on ?

Ok let me start this off by saying I was stupid. Very stupid. I was hit by a car whilst walking my little boy a few months ago. Was not on any contraception. Wasn't seriously hurt so decided to start the packet of pills I had bought before the accident. Started them on the day I was supposed to get my period but didn't actually wait for it to appear. That would have been about 3 weeks ago. Fast forward to yesterday. Had a little bleeding put put it down to the pill. Went to the bathroom and passed what looked like a sac. The bleeding became very light brown spotting after that and then stopped altogether. Showed it to my doctor and he said it looked like a miscarriage and I was quite a few weeks along. I've had some cramping since but no more bleeding or clots. Is it definitely a miscarriage and if so did my stupidity kill my baby? I'm in bits. We've had so much bad luck a baby, though unexpected, would have been so loved. I feel like I've deprived my son of a sibling by being such a fool