Any hedonist thoughtful enough to use the word "hedonism" probably has some rationalization for their value system, such as "It makes me happy." But this begs the question "What is the metapurpose of happiness?", or why should I want to be happy? That brings me to what I believe the original question was getting as, which is "Does every purpose have a metapurpose?", or can we always know why we want something?
I think the answer is no. A few moments of introspecting our value system the same way a child might pester an adult (Why? Why? Why?) should bring us to a question we cannot answer. Alternately, we can note that if every purpose had a metapurpose, then our value system would contain either an infinite regress or a circular loop. At some point, we're going to need an axiomatic purpose, or something we do just because we feel like it, with no further justification.
At that point, the question of "why" breaks down into the questions of "how", in that a normative question has no answer and instead leads us to a descriptive question. We cannot ask "Why does this feel good?" in the sense of "Why should this feel good?" Instead, we can ask "Why does this feel good?" in the sense of "How did this good feeling originate?"
Then we can answer in terms of the biological mechanisms of feeling, and in the case of instincts, the evolutionary processes that caused those biological mechanisms. In the case of learned feelings, it may be more useful to answer at a level of abstraction which supervenes on biology, that is, in terms of psychological processes and formative life experiences. The really difficult part is separating instinctive from learned behavior.