I'm really not sure. I should have started my period yesterday. I'm very athletic, I'm only 18, and I've never been in this situation before. I've heard you should take it a week after your supposed to start?

Nope, you need to wait AT LEAST two weeks after you miss your period.
Then be sure and use first urine of the morning as soon as you wake up.

If negative and no period, test again in another week.

Thanks :)

Maybe this is what your boyfriends parents were worried about. Looks like they may have had cause to worry.
You'll have to wait 2 weeks after a missed period.