Ectopic Pregnancy

Hey girls. So im now 8 days late, had a BFN at 4 days late and still have several several pregnancy symptoms. But i have a pain in my lower right abdoment thats just hurts all the time. Well my lovely coworker (who just found out shes pregnant) oh so nicely said to me 'Maybe youre having an ectopic pregnancy!'(like it was something to be excited about). But it got me thinking about it. Have any of you had this happen? How did you know??