Is it possible to get pregnant if hcg levels are above 100 after a recent ectopic pregnancy? how low would they have to be to ovulate again?

Zero: You need to wait until the HCG reaches zero to try again. That is for several reasons. First you could be at danger from the ectopic still if is not totally gone. Also after a miscarriage or an ectopic it is possible to have a type of pregnancy cancer where the HCG never goes down to zero. So in either case it is very important to follow the HCG down to zero first, .