Your post really helped inform me as to what could have been going on, thank you so much
Some women can be pregnant and get their periods. This is kind of rare though.
The only way I know of to find out if this was a miscarriage would be to see your Dr for a blood test. If you were pregnant the hormones would show up in your blood.
This happened about 3 weeks ago, right? If so, your hormone levels would be back to normal by now so a blood test would not help at this time.
The other thing I was thinking this might be is implantation bleeding.Not all women get this though and if they do it's usually very light bleeding. It happens within a week of unprotected intercourse, if it's going to happen.
When are you do for your period? If it's late or seems unusual take a pregnancy test.
I wish I could have answered your question but it's too late to know if it was a miscarriage or something else going on.