LOL! Can't believe my first post is about burning pee... but here it is: soap! Yes, it's probably a chemical irritation from soap getting inside your pee hole. If you do some creative google-ing, say for "what makes soap burn penis", there are a bunch of links, some answered by docs, or health care peeps, but it is a fairly common thing. Kids get it a lot, my first time was about ten years old. Some soaps are mild, like Dove, others have way too much caustic chemicals in them, and will even irritate the outside of your sensitive areas, let alone the inside. It's probably not VD. Just some soap getting in up there.