Pill side effects - bleeding/spotting

So a week ago I had to take the emergency pill as the condom slipped half off and I didn't want to risk anything. Yesterday I had some pink spotting that then turned to dark brown light bleeding (similar to the start of my period) but today its continued to be light bleeding but very dark brown still no red or pink at all.

My last period started on 29th December and I had to take the pill on the 8th January (so only 11 days into my cycle, not yet at ovulation). But is it odd that its taken a week to get this bleeding from the pill? And why is it so brown like old blood?

I've now been given the POP (Progesterone only pill) to use for contraception instead of condoms. But my GP told me to wait until I got my period or a negative test first. I'm guessing this bleeding is just a side effect and not my periods that come 2 weeks early? (Which mine never come early, if anything its usually a week late).

Any friendly advice appreciated! Thank you 🙏🏻