Z.A.
On the "buy a test in a week" crowd...my son was conceived on BC pills (I'd been taking for 5 years straight without missing a pill), while using condoms with spermicide. He reeeeally wanted to be born.
So, too....eating a lot of soy (esp. edamame beans, darn I love those things), can trigger pregnancy-like DANG that HURT!!!! effects with my breasts.
Cysts or a strained back (go figure, as if hurting your back wasn't enough) or a pinched nerve, or many other medical reasons can cause breast pain. I would personally: wait a week (yeah right, me, I'd buy 2 tests one for now and later, because I'm paranoid), take a test, and then call the doc.
So tough, though. I'm right with you for 2 days straight every time I hog a whole bowl of salted edamame. Mmmmmm. If only they didn't make me hurt.