My I have had 2 mmc now and my periods were 28-29 days with a flow of about 4-5 days after 1st mc it took 6 weeks for af to show her face and she was different I now can count sore boobs as a symptom of af and my cramps were less. my second cycle was 30days and only bled for 4, I fell pg that cycle.
After the 2nd mc, it again took 6wks for af to return, af was lighter and only lasted 4 days, I had a cycle 30days later that went for 4 days but had a small amount of blood/discharge 2 days after af stoppped, I didn't have any cramps just sore boobs and this cycle started technically 30days later but started with brown spotting and then gradually got heavier I am currently on day 6 and af is tapering off but is still there. My flow was much heavier this month had the sore boobs but massive cramps .
As you can see it can be a little all over the place and all different symptoms, flows and all that. I know they say you can try again straight away and a lot of women successfully do but I think waiting a few cycles can help the body recover. I feel like my body is regulating itself and clearing itself out.\
As for drs telling you CD1 is the day of your DnC or mc I also think that is wrong. A lot of first cycles after mc are without ovulation and it can take 4-8wks on average for af to come back. it can also take several weeks for hcg to return to low levels. From what I've read on here most things are normal and just hormones being out of whack and your body getting back to normal. I would only worry if af doesn't come back and is super light/heavy, then see your dr but all in all ladies everything is normal just not normal for us.
It's horrible after the pain of a loss our bodies trick and confuse us for months afterwards.
I wish you all the best of luck