How would you know if you had a chemical pregnancy??

The reason I ask is from my other thread about the First Response HPTs. I do believe that I had a positive HPT at 9 & 11dpo especially because I had a lot of cramping, back pain and extremely sore pains going through my boobs at that time and I never ever have that in my cycles. AF still hasnt shown up making me on CD30 which is really strange cause I always have 25/26 day cycles.

So it makes me wonder if maybe it was a chemical pregnancy cause yesterday, 13dpo I got a BFN.. Is there any way of telling or is it always a mystery? If AF is heavy & clotty would that mean it was a chemical pregnancy???