If I am in a monogamous relationship why did I have a foul odor the day after intimacy?

I have been in a monogamous relationship for 5 years, I haven't been on antibiotics and I'm not diabetic so I don't know why I would have this happen. I also had frequent and painful urination. I Immediately started drinking a lot of water, using betadine to cleanse following with vinegar and it went away after a day and half. This happened twice in a 6 week period. I don't know if I should be accusing my SO of being unfaithful since it wasn't an infection, at least I don't think it was. We usually have oral interaction during intimacy could this have something to do with it? Boy, I'm glad you don't know who I really am, cause I feel really naive (dumb). I have brought it up to my SO and he says he noticed it also but he didn't want to say anything as to not to offend me. He denies any other intimate contacts.