Positive test, seems too soon.

Hi all,

I had a missed miscarriage, and took the medicine the week of Christmas. I got my period exactly on time the following month January 21st. It lasted 4 days. I was already showing some of the same signs I was last time, so even though I don't get my period for another two weeks I took a test. It came back positive. Is this even possible, or could my hormones still be off even though I got my period last month?