What else could it be? Please read. Females.
I know there's a HUGE possibilty that I'm pregnant. Me and my bf had sex the day before and the day after I ovulated and sperm stays in ur body for 72 hours, and I have yet not started my period and I was suppose to have started Saturday. I took a pregnancy test yesterday but it showed invalid. (cheapo $1 test) I know there's a huge possibilty that I am pregnant but what else could cause a late period. (pretty sure I'm pregnant because for the last 3 nights I have had heartburn so bad I couldn't sleep and I had heartburn at night with my first child but I just want to know all of the possiblities)