Boyfriend is expierencing burning?!

My boyfriend and I had sex last night and right after he finished he said his testicle region was burning. We have used Plan B 4 times in the last 2 months.. maybe that has something to do with it? He thinks it may be from me. He also said it may be because he just shaved.. I am sure that is not the reason because we've certainly had sex right after he had shaved before. If it is coming from me does anyone have an idea what it is and how I can get rid of it? I feel perfectly fine but he says that he feels burning after and notices an odor. Help!