Chemical pregnancy?

I have a regular 25-day cycle and use Glow to predict my ovulation (so I don't know for sure when it was). My OH and I had sex on 10 and 11 of June - the day before and day I was due to ovulate. 
On the 16 of June I noticed some light brown spotting but it went away by the next day (only saw it when I wiped). 
I was due for my period on the 24th and my periods are regular. On the 21st I started to bleed. It came on very suddenly and while it wasn't as heavy as normal AF it was more than spotting. It didn't fill up a tampon though and then disappeared overnight. The next morning it had come back again and I noticed it was very thin - not like normal AF. The day after that it was back to spotting again and then just stopped - no brown discharge like at the end of my usual AF. 
I thought maybe AF would come for real but it just hasn't. 
A couple days after it ended I started getting cramps and lower back pain - with some pelvic and hip pain for about 1.5 weeks now and it won't stop. I've been mega tired too and very snappy - feels like I'm PMSing but no spotting or any sign of blood. 
I checked my CM yesterday and it was egg white like so I guess I'm ovulating again (just as Glow predicted I would). 
I did take a few pregnancy tests a few days after the bleed and they were all BFN
I'm wondering if it could've been a chemical pregnancy? Or is it more likely to be a cyst or infection? I've had multiple UTIs in the last and have no painful urination so I don't think it's that. 
I didn't test before the bleed - I was a bit nauseous beforehand but that's not rare for me.. I have a weak stomach to begin with so figured I'd eaten something funny. 
It's not severe just uncomfortable.