BFP, followed by BFN, then AF shows up😢

Sorry it's so long, i just need to vent😔.. So as the title says, I got my BFP on 15dpo, one day late. I was over the moon excited.. I have PCOS, and we've been TTC for 2 years now, and this would've been my first pregnancy, no other losses.. I tested again, 16dpo, line was still there..but it was  a little lighter than previous day, and I just knew something wasn't right:/.. I was feeling super gasy, constipated, crampy, and my face, hands, and feet felt swollen, up until then.. So I waited 2 days to test again to make sure hcg got the chance to double, but in my gut I knew it wasn't right, and my symptoms started to subside, and the cramps felt different.. So I tested at 18dpo, and I got a BFN.. AF started that day, which was yesterday.. Now I'm bleeding more than usual, and I'm passing more clots than I normally do.. I just assumed it was a chemical.. I have a doctors appointment today to see what happened..