Is every type of happiness or pleasure explainable (possible to articulate through reason or logic)? Should I be distraught that I am unable to articulate clearly some of my pleasures? And does an unexplainable pleasure (if it exists) suffer from its unexplainable nature or flourish because of it?

Approaching your question a little differently, one might ask a further, pragmatic question, to wit: what difference does it make in your life (to your happiness, to your sense of well being, to your life projects) to experience pleasures/passions that remain inarticulate or not fully articulable? If the inability to symbolize a passion, or to capture it in a string of sentences causes you a measure of suffering, then it makes sense to attempt an articulation of it or to ask why that matters to you (therapists -- of the psychoanalytic persuasion, among others --make their money engaging in just this form of labor!) On this more pragmatic approach, the issue would be less whether one "ought" to be more clearly representing ones pleasures to oneself in order to experience them more completely (in some sense), as an embodiment of the maximally good life, but rather whether the existence of specific non-fully articulable pleasures/passions seemed to you (or to you in relationship) to be preventing you...