First month TTC...BFN

Hi all! I wanted to hear if anyone else has had this... so my first month TTC my period was 2 days late and I'm always on time, I started spotting pink mucus that turned into brown (sorry tmi). Eventually that turned into full on AF. The thing is my period is so so bad and usually it doesn't bother me at all. I really felt pregnant, I was so crampy all month, had some other symptoms but I tested the day before AF and got a BFN. What I wonder is why is my period so bad?? Was something maybe about to take place? I'm 4 days in and still such strong cramps. On a side note while checking for blood last week I felt a lump that today has gone. Now wondering if a polyp burst and that is adding to the heavy flow and cramping!? Any advice or similar stories would be appreciated x