Extreme tailbone pain in early pregnancy/early BFP

I’m unsure how far along I am but according to glow I’m 3 weeks, 1 day (super early to even have a BFP). It’s possible that I ovulated early but my last cycle started 1/21 (unless that was 3 days of very heavy implantation spotting but I really don’t think implantation bleeding could be that heavy).

I had this gut feeling that I was pregnant so I tested early and got a faint line at what I thought was 5DPO. 2 days later that line is darker and I have developed extreme tailbone pain with absolutely no history of trauma. It hurts so bad that I wake myself up at night and it’s hard to get in and out of my car.

Has anyone else had this early pregnancy symptom or is it possible I’m further along than glow thinks? I haven’t called the doctor yet since it was such an early BFP and wanted to wait until I was confident I was pregnant.

The only other symptoms I’ve had were cramping, VERY light implantation spotting (barely noticeable), and extreme fatigue.

This is my BFP from what glow predicted to be 5DPO

BFP at what glow predicted to be 7dpo