So many periods

I finished my period on december 17, and that period was horrible. I could barely function for the first three days I was in so much pain which is very unlike me. After this period I also always had a pink/brown discharge. I had unprotected sex on December 24, and then on December 31 I started bleeding again like I was having another period. My period are always 4 weeks apart so getting it again was very strange. And that pinkish brown discharge that happened between my two periods was also unusual. Could this be pregnancy or what?