4 day early period and other weird stuff. TTC

[BelleAme]

Okay so SO and I had unprotected sex on the 10th and I began an what seems to be early period on the 19th. My period isnt due until the 23rd. It was very very light for the first 2 days and then today the 21st its a bit heavier. Ive had cramps since day 2 and they've been worse than normal. Generally by day 2 of a regular period my cramps have subsided but not this time, I'm still not completely filling a tampon like normal either and there is a mix of brown in it as well. I'm usually on time or 1 day early/late but never 4 days, I should add my period the last 2 months have been odd since TTC. Now on day 6 of this weird period I TMI have blood in my stool and have cramps but only have brown discharge on tampons. I read that this can happen with pregnancy but I'm worried