Both.
Yes it is possible to ovulate.
Ovulation occurs approx two weeks before a period is due.
(you actually ovulate before your first period, which is why even if you haven't started your periods it is still possible to get pregnant)
it would seem a little early to ovulate (4 days after) but not unlikely.

Lots of women are said to be much more fertile in the first couple weeks following miscarriage or birth.

The cramps could just be your uterus contracting to get back to it's original size.
If they are just like period cramps they are likely to be nothing to worry about. If they get worse or sharp, or if you get shoulder tip pain, shortness of breath/chest pain, fever or blurred vision then go straight to the er and tell them that you recently had a d&c for miscarriage