Ecp-withdrawal bleeding

I took the ecp about 10 days ago, I start bleeding very heavily yesterday and it lasted around 24 hours, heavy enough to fill up 3 sanitary pads even. But it stopped today, it's been over 17 hours since I bled even a little bit. I'm confused because isn't withdrawal bleeding supposed to happen 5-7 days after ecp and ATLEAST last 3 days? Could this have been implantation bleeding or was it too heavy? (For context I had to take 2 full doses of the ecp a day apart because I had unprotected sex after the first one again. So my cycle is EXTRA messed up)