My period is due tomorrow(10-15-10), but I don't know if it's going to come. I've been having minor cramps and have tender breast, but not too bad. I've been REALLY tired lately and my appetite is changing. Could I be pregnant?

Did you have unprotected sex? Then the answer is you could be. You can only really guess. Although it is frustrating, all you can really do now is wait and see if you get your period. If your period becomes a week late, then take a test but bare in mind that it could show a positive result so early on.
On the other hand all of those symptoms can be related to an approaching period :)

Hope you get the result you want..