Cause for concern?

Hi! So I’m currently on birth control, the pill, and I take it at the same time everyday minus a few times where I’m a couple hours late. In November I ended up having sex with this guy. I didn’t want to have sex with him so it’s a long story.. However, because of that I ended up taking Plan B maybe like 9 hours later because when I woke up at his apartment he wasn’t there and I didn’t know if he used a condom or what even happened because I was under the influence when he took me to his place. 😔 He told me days later he did not finish inside of me but didn’t use a condom. I took plan B Nov. 19th and ended up receiving what I think was my period in December 1st. I had cramps and it was red and lasted until the 8th. I receive my periods on the 4th week of my birth control pack because that’s the placebo so I got it during that week which was normal.

However, this month I don’t know if there should be a cause for concern. Usually I get my period around the 2nd placebo pill but I didn’t and I’m on the 4th pill. I checked just now and I have dark brown blood on my underwear but when I wipe there isn’t a lot. Is this my period? Should I be concerned about pregnancy/take a test? I haven’t had any pregnancy symptoms other than bloating, hunger, peeing more frequently but just stared getting cramps and back pain.