Another discharge question

I know this might be stupid and absolutely weird to ask. But I've had unprotected sex (using the risky pull out method) on my last day of period while I was spotting. I'm getting a lot of brown discharge as, I usually don't have this much brown discharge, I'm slightly concerned. Also I'm getting sharp pains in my stomach but that just may be because I've finally started working out 😂 Anything to worry about or is it just old blood? Thank you