Has there been any recent change at home, i.e. has the new baby arrived yet ?

My son went through a phase of taking off his diaper at night time very shortly after our daughter was born; thankfully it only lasted for about two weeks.  To get him to stop, we used duct tape to secure the diaper on him (to cover the diaper tabs so that it could not be taken off), telling him that this was 'magic tape' that would help him to keep his bed dry.  On the first night he thought this was great, like a superhero's belt.  The next night, he complained a bit, but we told him that he needed the tape, because of the bed wetting.  On the following (third) night, when he complained again, we told him that he could skip the tape, but only if he promised to not touch his diaper.  He agreed, and it hasn't been a problem since then.  The duct tape roll was placed on the top shelf of his closet, where he could see it, so he periodically sees it and reminds us that 'you shouldn't touch your diaper at night time'.   

I know that using duct tape might sound extreme, but it worked, and was suggested to us by several others who said it worked for them, too.

I hope this helps !