Pregnancy test

I had unprotected sex on Christmas Day but I am on the pill. I just haven’t been taking my pill at the same time everyday due to my work schedule. My period was due on the January 1st but I got it December 31st and I am not sure if it was a period. It was dark brown discharge all over my pad. Then after two days of dark brown blood it was dark red for a day and now I have light brown discharge. I’ve never had a period like this. Could it have been implantation bleeding? I don’t know if I should take a pregnancy test or just stop worrying.