What should I do?

A bit of a disclaimer; this could be a little tmi but I’m confused and need to get it out of my system.

I was seeing a guy and we had sex on Sep 23.

I masturbated in a new position on the 29th and noticed old (brown in color) blood when I cleaned up.

My period was due on the 30th so I was thinking the old blood was part of that (my first day is usually pretty light and day 2 is much heavier).

The heavy day never came though; I was brown spotting for