Difference between a period and pregnancy.

Hello, Please help me. I'm 21...and I have had protected sex I'd say about a month ago. He wore a condom. I'm not on birth control. I have had pretty much regular periods up until this month. It came when expected. Friday/late night I started. It started off the way it usually does (red/brownish, somewhat black if I remember correctly) and then as it continued onto Sat. and Sun. it was quite heavy. I was even experiencing some clotting, big gobs of dark blood, looked like black raspberry jello or something! Anyways, but then once Mon. and Tue. came...it slowed right down, almost to a complete stop, and now today (Wed.) I'm spotting redish/brownish spots when I wipe after going pee. I don't know whether or not to think this is normal...as in-an irregular period, or what? I've read that even pregnant woman have their period...but does a pregnant woman bleed as much as I did for the 1st couple of days of their 'expected period'...is this just my period? Please help...I've been looking for help all over...but I keep getting different answers. This is the last time I seek for help...hopefully this final answer will put my mind at ease... Am I pregnant despite this period? THANK YOU THANK YOU!!