The same thing happens to me! It used to be worse in the 1st trimester. I would wake up a couple of times a night. Nowadays it's the 3:40am bathroom run. i wake up on my back too, sometimes with my legs bent and then I have a yucky feeling and then I know I have to go to the bathroom. I don't get the usual I need to pee feeling from before I was pregnant. I gethead aches too now in the middle of the night and it takes me awhile to go back to sleep. I've found the best way is to shut your mind off and focus on going back to sleep and nothing else. Chatting makes the next day worse, I used to do that and it's not worth it