I think you answered your own question: these things, although pleasurable, don't lead to happiness. The confusion of which you write is the cause of much unhappiness.

Am I happy that I ate too much fatty, high energy food? No. Did I find them pleasurable? Yes. Are drunks happy? Usually not, as their lives become messes. Do they find getting drunk pleasurable? Yes. But it's the fact that they can't tell the difference between pleasure and happiness that ultimately leads to their pain (assuming they aren't genetically doomed to develop the disease). Those who forego responsibility to engage in sensual pleasures too often end up very unhappy.

EDIT: Type to -> too in last sentence