Miscarried in dec within a week had paragard inserted, no period, i had a week of spotting and cramping. when should i be concerned with no period?

Soon: We usually expect you to resume normal monthly cycles about 6 to 8 weeks after a miscarriage. That assumes that you were regular before your pregnancy? It's not unreasonable to check a pregnancy test and make sure that your pregnancy hormone level resolved to negative after the miscarriage. If your miscarriage was incomplete, that would also delay your next period.