light bleeding for 4 days now what could be the problem

Hi I'm 20 and my last period was 19/06/07 it lasted the normal 7 days i have a 26 day cycle, i had unprotected sex on the 13 day of my cycle and a day later i started bleeding lightly, not even enough for a panty liner it only showed up on toilet paper. i figure probably mid-cycle bleeding but this is now day 4 and i'm still bleeding EVERY TIME i go pee and the blood is increasing steadily. i'm not sure if this is normal bcuz if it is ovulation bleeding it's my first time, but i am really starting to feak out here. so if someone could pls shed some light on my little situation i would be grateful. my next period is due a little over a week and i'm never this early
Thanking u in advance & All the BEST