What Causes Itching In The Urethra?

Hello. I am writing because a couple of days ago my husband began having an itchy feeling inside his urethra. No pain during urination and just called to let me know that there is also a slight clear discharge coming from the urethra. We have only been with each other, no known std s , except for the fact he had been diagnosed with gonorrhea about 7 years ago and was treated. I asked him if he thought it could be from masturbation ( loation/soap) but there has been nothing out of the ordinary. The only other thing is that on and off for the past few years, when we have sex, he will have a burning sensation from me ( I have been tested multiple times for everything under the sun and everything has come up negative, believe it is my PH balance at times that will cause this issue. There are no rashes or anything afterwards and it will go away after cleansing) . Any thoughts?