I see this as a significant difference in perspective:
There is no pain or pleasure apart from the two feelings. I'm not saying you are intentionally, but your phrasing makes it sound like there is some abstract absolute thing called "pain" and "pleasure." There is no pleasure apart from the feeling of pleasure; there is no pain apart from the feeling of pain.
Before I begin, I'll note something that will quickly become obvious - that this argument, which is ultimately about feelings, pathe, is also an argument about words and definition, and about how language is used and how it should be used.
And while I am not ready to state a final formulation myself, I do see my question in the latter light: It's true that pleasure is a feeling, but it is also true that "pleasure" is a word signifying a concept, and we have to be able to deal with both perspectives.
"In Epicurean theory, is ANYTHING in life (even desire) always pleasurable except pleasure, or is anything always painful except pain?"