Well... I don't know as there's a lot I can tell you about this. I'm an older man myself. I have to get up to pee every couple of hours or so! Since, from what you wrote, it sounds as though you've had yourself checked out medically, perhaps this is simply stress-related. Other factors could include the amount of physical exercise you're getting & the amount you're drinking, or what you're drinking, during the evening. (Acidic beverages can have an irritating effect on the bladder, or so I've been told.)

Sometimes I can't get back to sleep after getting up to pee. When I can't, I typically get up & do walking meditation for an hour or so. I just walk slowly throughout the dark & quiet house, around-&-around. I focus light attention on each foot as it comes into contact with the floor. Thoughts come-&-go. I simply allow them to arise & fade at their own pace. I hear the sounds of the city off in the distance. After I've walked for an hour or so, I go back to bed & I typically go back to sleep. I typically don't notice any increase sleepiness the following day. I enjoy this so much that, when I haven't had occasion to do it for a while, I start to miss it. Anyway these are my thoughts with regard to your post. Good luck figuring this out!