O.k. here's the deal. My boyfriend and I decided to have sex. Upon the both of us finishing, he wanted to go again. He didn't pull out of my body and we used the same condom as before. Is there a chance that the condom could have failed? It also shifted slightly up, but from what we could tell, nothing leaked. I am on birth control as back up, but it's a lower dose. Should I be worrying?

Condoms are designed to be used ONCE only.

No, They have a high failure rate to start with, you will only greatly increase their failure rate by doing this.

Bad idea, at the very least check to make sure the condom worked properly, and don't take a chance it will survive longer than it has. As others have said, its not 100% reliable in the first place.