Sex for pleasure is not wrong. God made sex to be a wonderful thing and an enjoyable thing, it's society that has perverted it. God also commanded that sex was to be exclusive to a married relationship. So sex outside of the realm of marriage for any reason is wrong. The pleasure in itself is not wrong, it's the circumstances in which you receive the pleasure that counts.
As far as touching yourself goes I believe not masterbating is about self-control and honoring your temple (your body). I don't why we have wet dreams. I do know I never started having them until I stopped masterbating. I also know that when I have wet dreams that they're not always pleasureable. Sometimes it just happens and I don't know that it happened until the next morning. So comparing touching yourself and wet dreams is comparing apples to oranges. A voluntary act cannot be justified by an involuntary action. You choose to touch, you do not choose to have a wet dream. So therefore you can't say that just because we have wet dreams (that we may or may not receive pleasure from it) that it's ok to touch.