Hi,
I don't think I've had the same experience with peeing...what happened with me was that my bladder for some reason needed some "extra movements" to emply completely. So, I peed, then when I went to wash my hands I noticed that I still needed to go for a bit more.
Maybe your babies are pressuring your bladder in a way that prevents it from emptying completely. Combine that with a little "nubness" of the sfinceters...you have a damp underwear.
If you are doing what the doctors said, you are having to deal with a LOT more of urine...I am drinking maybe 7 glasses of water per day and believe me, there are moments I need to run to the bathroom. If I sneeze...well, there we go!
Hope you feel better. The good thing is, the cervix is sealed and the babies are swimming in a nice pool of amniotic fluid
Wish every one else is doing fine! I am dealing with yeast infection - again. DH and I tried a bit of intimacy with hilarious consequences: the next day he was in a very bad shape!

Be well, Literatriz