4 year old waking for a wee every night - how can we break the habit?

[scampidoodle]

This started 3 months ago and was only 4 or 5 times a week but now it's evert night without fail. It's also got later and is now after 5am, which means he rarely gets back to sleep again so is permanently tired and this makes him very difficult and naughty.
After the first week we put a potty in his room, thinking he'd find it too babyish, but he didn't. We've been to the doctor but she couldn't suggest anything and he doesn't have a urine infection. It began when he started some new asthma medication but stopping the tablets for a few days has had no effect except making his chest bad again.
Any ideas how to break this habit?
Any advice gratefully received!

I dont think theres much you can do if he needs a wee he needs a wee!. Maybe try waking him for the toilet when you go up to bed then he has chance to go back to sleep and hopefully not need it again....he will soon grow out of it. Maybe cut down on drinks before bedtime aswell. My son still wakes for a wee 3 nights a week roughly and he is six. When you gotta go you gotta go! Good luck

What do you mean, "break the habit?" Surely if he need to pee he needs to pee?

Can he not just take himself to the loo or does he need you to help him?

It isn't a habit it is a need. Better that than wets the bed.

Think about it - he sleeps a long time so naturally needs a wee.

With ds, we would lift him or wake him when we went to bed. That saw him through until morning.

Thanks for the responses.
The reason we think it's habit is that he's been dry at night for about 15 months and in that time has only had one short spell of a week or so of waking for a wee, right after he started being dry. It definitely seems like a habit that he's got into, that he's waking and just getting up to wee straight away. He isn't drinking any more/later in the evenings.

Anyway, he didn't get up last night/early this morning so perhaps it'll stop being so regular now.