i have a 5 month old puppy and she is almost there with the toilet training but when she sleeps she wets herself and her hind end is always soaking although we wash her frequently we are afraid she may get an infection any advice as to how to stop her doing this would be appreciated

This sounds more like a bit of incontinence than lack of house training .  I think I would be tempted to get her checked by the vet to be on the safe side. - some young bitches can get a bit of cystitis, especially before their first heat