Nearly 2 yr old woken by (ahem) erections

[ProcessYellowC]

at writing this.
Since he was a baby my DS has sometimes woken up with his nappy being too tight because of an erection. Now its almost every other night, if not every night that he wakes/is unsettled in the early hours of the morning, so I take of his nappy, and his willy springs up! It is obvious that he gets instant relief.

I am using reusable nappies, but I imagine that even with disposables, by that time of the morning they will be so heavy and wet it won't help.

There's probably nothing I can do, but is this common? It would be great to hear if anyone else has/has had this problem!

My son did this MULTIPLE times a night. He still wakes twice a night, even now he's out of nappies at night. The first time is to wee, and usually it's the erection that wakes him up. The second time it's the erection that wakes him up and then he comes and co-sleeps and then probably wakes a few times but goest straight back to sleep without waking me.