Having you felt unsatisfied with mastubating sometimes? Or even if you have had sex, haven't you felt unsatisfied internally? Usually there's a time when people feel "the need" for sex (and I ain't speaking about the time you decided to just do it), when you can only think of it, even if you have done it a little earlier before, to the point that it even bothers you, perhaps.
Haven't you felt the need? How do you deal with it? Is it something that you have gone through, something that repressed people may have to deal with or something completely different?