exactly what sweetpea said.
A burning sensation that he feels does not automatically mean something is wrong with you. The discharge you have is normally acidic in order to prevent infections and other problems, so along with your diet it could have been more acidic that day/night when it happened giving him that feeling. If you had an infection, you would have other symptoms that would show that is the case(itchiness, clumpy discharge, pain, different odor, etc). It might also be that he is sick or has an infection himself and this has nothing to do with you. There are a lot of possibilities, so it's hard to say exactly what happened.