TTC after miscarriage...late for period?

Hi guys. I had a miscarriage (my first pregnancy) on March 20th of this year. I was about 6 weeks and 5 days along when I miscarried. The doctors said I miscarried naturally and I haven’t had a D&C; or taken any medication. I stopped bleeding about the 27th/28th of March and got positive ovulation tests on March 30th and April 3rd and then a negative on April 4th. I have still not started my period yet, but am getting totally negative pregnancy tests. Any ideas? Is it normal for a period to come pretty late after a miscarriage, is it normal if I totally skip this period, could I be pregnant again even though tests are still negative?