Maybe further along than I think?

Okay, so two days ago I got my bfp. We are so thrilled! Really couldn't be happier. Something inside me just told me to take a test, so I did and it was positive! Even though my period wasn't due until the 29th of this month. Well, I'm wondering if maybe I got pregnant in September, and not this month, because when I had my period on sep 29th, it was two days late (supposed to start on the 27th) and it was WEIRD. I bled really heavy with horrible cramps the first day and then just spotted brown for about 4 days after. So weird for me. I mean either way I don't care because I'm pregnant!! But I was wondering if anyone else has experienced this?