HUGS!
My son soaks everything often. He pees through his pull ups regularly. I usually have to change his sheets. He did this when he was in diapers too. I don't know what works. But I do know that there is a sheet saver pad that you can put in their bed over their sheets that is absorbent, disposible and saved me from having to wash sheets every day. They are usually where the big kids goodnights are. As far as keeping him dry, I have no solutions, but lots of sympathy. I think that putting the absorbent insert in may help greatly. Oh, and he may be holding it until he is absolutely full. DS refuses to poop at school usually, which means that time we hit the house, his pull up is full to the brim. Don't know why he does that, but that is my kid. best of luck to you. Let us know how it works out. Wow, it won't be long now until you meet your new little one!