I started my period on dec 12th and it was light for a few days until the Thursday then heavy until Saturday then real light and brown only. I had unprotected sex on the 19th.. Could I be pregnant?

Yes, you could be pregnant. Are you? You won't know until it is time for your next period.

Yea I know.. just thought someone might know the time frame and etc better then I do. I have been feeling more tired this week than I normally do, as well as cramps or discomfort in my lower stomach on the right side near middle today. I have been a bit bloated feeling as well today.

You may very well be feeling the beginning effects of premenstruation or even pregnancy. You just won't know until it is time for your next period.