Can you still ovulate with hcg still present? if so what is the number it has to fall to for you to be able to ovulate?

A small amount: A "negative" HCG test is less than 5mIU/ml and it takes about 4-6 weeks for your body to get back to or below this number after a pregnancy whether it be full term or miscarriage. It's possible to ovulate even with hcg levels still around 50, although this isn't common. It varies from woman to woman. I would start charting your CM and temp or use ovulation tests to know for sure.