Period is lighter, different colour?

Okay, I know I’ve asked this a few times, but I still feel worried, and I’ve not had a chance to phone my doctor cause my mum is always around, so can someone please help me here until I get the chance?

Basically, I had unprotected sex on the 26th of June, and took the morning after pill on the 28th. I’ve a really irregular period, but I’d figured out that it should’ve been coming around the 12th of July. Last week, around the 5th, I kind of felt that my period was coming, but normally it’s way worse. I get really bad symptoms, and it’s really obvious when it’s coming. This time it wasn’t. I had really dark brown discharge on the 5th, and then blood, so I assume it was my period, but it wasn’t like my normal period.

They’re normally much heavier, like really heavy, and this was barely noticeable. And it’s been a different colour. My period’s normally red, like blood. But this has been brown, and thick.

Could it be a side effect of the pill? Or something else, like implantation bleeding? It’s been nearly a week.