I can't tell if I'm on my period or not

This is the first time this has ever happened.

Basically, I've been worried about my period coming this month because I had to take plan b earlier this August.

I've been worrying thinking I was pregnant this whole time and once I woke up the morning and went to the bathroom I noticed a tiny bit of what looked like brown discharge. I thought 'oh, this is blood getting in the white discharge and I got my period'

But then later on I took out my tampon as it was basically clean.

Then I 'inspected' and there was blood. Not a lot but like it was there.

Should I be worried?

I have all my period symptoms, the only thing I'd say is different is my cramps. I feel like I haven't had cramps at all. Usually they're very noticeable but this is making me worry :/

I googled about it and apparently brown discharge can be a sign of early pregnancies.

But I took tests and I'm not pregnant.

Am I just worrying too much and it's effecting my period? Maybe the plan b affected it? Maybe I'm ACTUALLY pregnant?

I hope I'm not cuz I'm getting the contraceptive implant on the 5th of September and I won't be able to get it if I'm pregnant- I'd have to have an abortion and get my implant NEXT year.