OK, so I got an emergency appointment with the vet and drove 45 minutes to get there. Of course, by the time we arrived, the snake had peed and was no longer swollen lol so they booked a regular appointment for 12/6 and said call if it the swelling last more than a few days. My gut tells me he just has held back his poo from the last shed and the swelling gets worse when he has to pee because there is extra volume down there. And the constipation/holding back is causing dehydration, making him drink more water than normal, so peeing more than normal.
It sounds like it is normal for them to get puffy before pee/poop and it does go away after, so I guess the main issue is constipation so I will do some research on how to maybe assist with that beyond the lukewarm baths I have been doing. Thanks everyone for your replies!