Can I get pregnant after taking the plan b pill?

So I had sex with my sex partner maybe about a week ago now thing is we used protection so when I got off him the condom slipped of him and got stuck on me somehow lol Anywhoo we went and bought a plan b just Incase so when this happens I had gotten off my period and it had been 2 days since I got off it.

So 4 days go by after taking the plan b pill and I get my period again...so I just got off it today and haven’t had any sex since that day and my breasts just started to get sore yesterday is that normal hormonal change? I’m usually a regular and taking plan b’s have messed up my cycle before