Can someone explain this for me please ....

Okay so on the 9th my period had ended and it was a shorter period than I usually have and on top of that I didn’t really feel like I was on my period if that makes sense and it was lighter than usual. I had unprotected sex the 13th and after like in the late night this came out of me and everyday after this happened I keep spotting. I’m 23. I’ve never had spotting while ovulating or spotting between period or anything like that. I usually just have a heavy period that lasts for 8 days and it’s always on time no problem. Also my period had came 5 days early? And it NEVER does that. It’s like clock work it comes on time every time. Someone please explain.