I'm sorry rain, I'm not sure what to say to help. I think you just have to keep working through those feelings and talking about them to anyone who'll listen. A bit like the bear hunt, you have to go through it.
My dc4 was stillborn 10 months ago now, and for a time I felt very much as you describe, with it all going round in my head and me feeling it was all my fault. My fault that I didn't prevent his death, pick up something was wrong (after all, I'd done pg before, I should know, surely?!), my fault that everyone was so sad and that my other dcs know about death and such sadness, my fault that what should've been so happy went so wrong, everything felt like I should've been able to prevent or fix it. But I don't feel like that now, even though I still feel terribly sad at times. (I bet, actually, that you don't think it's my fault, do you? I bet you only reserve that blame for yourself).
Some of the things my mw said helped me - that there are times when they see someone during the day, and everything is fine, and then they lose the baby later that day. If they can't predict it, why should we?
I had a scan about 10days earlier, and although they thought it was possible growth had slowed, they weren't overly concerned. I figure if they couldn't tell something was wrong, why I should I be able to?
I thought about a conversation I'd had that earlier that day with my sil, where she asked about his movements and I said he was quite a quiet baby - he was, should i have been more worried then? (well in hindsight i should). But I wasn't, because one of my other dc - who he looked just like as it happens - was so quiet i was forever drinking cold water to check he was ok. And he was fine.
How was I to know? The fact is I didn't know, I thought things would be fine - why wouldn't you at 36 weeks in a low risk pg?
Another thing that has helped over time has been to realise how common it is. 1 in 200 births is a stillbirth, ten times as many babies die around the time of birth as from SIDs. So many people - friends of the family I've known for years, colleagues, parents of my friends, so many have lost their babies. I never knew before, because people don't talk about it. It's not just me, and it's not just you; sometimes babies die, because something goes wrong. And it's not your fault. Xx