What’s happening?

I’m on the pill (over a year) recently I’ve been more sexual active. My period is expected in 10 days on the (21st) yesterday (10th) I’ve noticed brown spotting and on the 9th I noticed bleeding after sex, today (11th), it was like I had a mini period, for 1-5 hours I was bleeding heavily with a big clot of blood, now, when I changed my pad, after 4 hours, only some spotting of blood is visible. Is this implantation bleeding?