Abnormal bleeding?

So my cycle is basically like clockwork each month and I usually start on the 28th-29th (30 day cycle). I stopped birth control in October and in November I had a regular cycle with no problems. I had unprotected sex around ovulation time which is fine. The odd thing is that I started bleeding 3 days early this month and it started off brown/pink and the next day it had small clumps and was heavier. I’m still spotting i guess but idk why because my pregnancy test said that I am not pregnant. Anyone had a similar experience? My appointment is next week..I’m going nuts! Lol