I would go get a test. I mean, i want to say you arent pregnant because you had a period, but women have been known to "have a period" during pregnancy. I even had one when i was pregnant the first month.
If you go to the dollar store they have very cheap tests. I think i saw one for 75cents. I would get a few and take them in the morning.
Are you trying to get pregnant? Have you taken a test at all?