Unusual period after a BFP? (Possible TMI)

Hi, I’m new to this app. So 2 weeks ago I took a test and it was a positive result. I was absolutely delighted! Then the day after I started brown spotting. The day after that I had a very light bleed - not enough to fill a pad. Then more brown spotting the day after and it was over. I’ve been under the assumption that I’m not pregnant since then but I just can’t let this go for some reason. My periods usually last 5 days and they’re heavy. Anyone with similar experiences??