Hi, My fiancé says it burns his penis when we have sex. He says it doesn t happen every time but every so often. I have been in a faithful relationship with my fiancé for 10 years and these instances of discomfort have been happening since we started having sex many years ago. He said it feels acidic but I know I do not have kind of infections. We have both been checked for STD s in the past. Could he be allergic reaction to my secretions? or could it be a specific time of my cycle where my ph is different? Also, I know it isn t due to chaffing or rubbing because aroused and lubricated when it happens.