Yea, your average healthy person will have decreased kidney function and urine production while they are sleeping. The reason I have this problem is from my competition days-I would get up like 5x a night to piss, it took a long time even after the competition to stop doing that. Do you actually have to piss everytime(a substantial amount I mean) you wake up or are you just in the habit of waking up, feeling the urge, and then going to the bathroom because you know you won't be able to sleep again unless you do-like a ritual?
My knee jerk reaction is to say that you should try living an impeccably clean lifestyle: no supps, no drugs, no alcohol, no bbing type lifting, no bbing type diet, do cardio and go in the sauna. Your liver and kidneys are working doubletime for a reason and their function is to keep you clean for the most part...so help them out.
In addition to that, if you find that you don't actually have to piss everytime you wake up, but you do so out of ritual, I would sacrifice a couple nights sleep(I know that's hard), ignore the desire, stay in bed, try to sleep until you have to get up again in the morning and THEN go to the bathroom like a normal person.
Maybe you've already done all these things, I don't know.
