I'm on the exact same boat. I'm going in to talk with my mentor next week to think concretely about a Plan B since I've been getting so many rejections--something I knew I might have to do, but didn't really consider it. Similarly, I've gotten only one interview so far. As disheartening as it is, maybe we can think of it this way: we're able to spend all of our time focusing on nailing this one interview (researching our PI's, coming up with great questions for why we're interested in this specific program, etc.). If this one school is my only avenue to grad school this year, I'm going to spend the next few weeks really understanding and falling in love with their program so that the interview can be as genuine and successful as it can be.