Overly long (and early!) light period??

Hi all!

Just wanted to know if anyone has had a similar experience. Apologies for the long post in advance!

My period is generally on time (give or take a couple of days), goes pretty much the same way each time (sore boobs a week before, cramping day 1 and/or 3, heavy 2-3 days before lightening up and finishing 3-4 days later). This time, it was roughly a week early, started kinda medium ish flow (with small clots) for the first day, maybe 2 days, and it’s still going days later but with barely anything coming out! It’s been almost 2 weeks since then and I am still getting a bit of dark brownish blood/discharge but only really when I wipe down there.

I had protected sex probably about 2 weeks before this period started, and I’ve taken a couple of tests. Both were negative, but I experienced some back pain yesterday quite suddenly while cleaning our bathroom. This is gone now.

So of course in my googling the internet told me this could be all due to implantation but the negative tests are telling me otherwise. I’m hoping to see a doctor this week and I’ll try another test next week but just thought I’d put this out there to see if anyone could put my mind at ease (ish).

I should note that since January I’ve been going to boxing classes pretty regularly (irregularly from last August-December) and have noticed that I’m a bit fitter, so maybe that’ll be it?

I also started this period at the same time my friend was due to start hers only hers started more roughly around the time I should have. Maybe a sync up gone wrong?

xx