CD 37 brown spotting no period

Been spotting brown for the last three days (not today) and only on the paper when I wipe, total TMI. I thought I had ovulated 9/10 days ago because I had a really close to positive opk (closest to positive it could be without being positive) and it got ALOT lighter the following days where the line was barely visible. Today my opk looks like this but I had a negative HPT yesterday. Any ideas why I would be spotting brown, having AF cramps but no AF? I'm so confused and worried there's something wrong with my body😭 Opinions or similar stories would be so helpful!