When you say you haven't heard from them, does that mean that you never interviewed, or that you interviewed and then never heard from them.
If you haven't interviewed, you should probably retake the MCAT. You are most likely not going to be accepted this year.
If you have interviewed, you still have a chance when the final date comes up for students to turn down the schools they have been accepted to and are not going to attend (I think it is May 1st?)
What, by the way were your MCAT's? Re-taking them is largely dependent on the score you received and whether you think you can do better.