For me it was a lack of symptoms that made me think I may be pg. I had always got sore nipples in the week prior to getting AF but I didn't get that. I had got a +ve OPK so I new roughly when AF was due. I had no other symptoms. I got a +ve HPT on DPO11.

The sore BB soon changed but I think I'm lucky they are not as sore as others describe I can lay flat confortably.

Anyway lack of AF symptoms were my clue.