Chemical Pregnancy?

Hi so I got my bfp on Sept 9, 10, and 11. I felt different my back was hurting and I had extremely sore boobs. Well on Sept 12 I started to have cramps like af was coming as well as some brown spotting. It’s Sept 13 and cramps have gotten worse spotting is getting heavier and I’m becoming extremely nervous. Af is supposed to show tomorrow but I’m hoping things are going to be okay. My bfp seems to be getting darker by the days so I’m just not sure what to think. Any advice or experience with this is much appreciated.