One of my good friends applied last year and didn't get in to any MD-PhD programs until July! You need to try to stay positive and keeping moving forward -- at worst you have to wait until July and start the process again. You at least had a number of interviews this time around; try to find out which aspects of your credentials you need to work on the most, and then just make yourself do it! If you turly feel that this is your calling, you will make it eventually. I'm not saying it's easy, but it isn't impossible. If anything you will have the advantage of knowing exactly what's going on in the next round. Try to stay positive.