Hello! I am sorry for your loss! I, too, just m/c'd on the 7th, I was just over 4 weeks.
The answer to your question is this....
It is hard to predict when you will O again because it depends on how far a long you were. The further along you were means you had a higher hcg level than me and it will need time to go down to around 0.
Also how long were your cycles normally.
For me I O'd on cd 13 which was Friday and I normally would have a couple days before.