Am I worrying for nothing (pregnancy related)

Hi there, I would have posted this on a pregnancy website but they’re so intimidating. Anyway here’s the details, I’d appreciate your help, but I realize there’s only so much you can help me with…

Protection was used, but really it’s all a blur thanks to my little friend alcohol. (I know, how irresponsible). That was about 3 weeks ago now, got my period on time sort of normal flow then stopped after 2 days with some light pink and brown bleeding the day after that. I told my doctor and she seemed to think there was cause for concern. I read up on it after that, and it sounds like implantation bleeding? Even though it was on time. I’m only 20 so this is scaring me. Also been feeling very tired and needing to pee a lot, some cramps too. I have to wait a few days before I test. Should I be worried? Thanks for reading.