I may be alone in this, but I continue to think that desire is a kind of pain. We feel it as pain because we feel it as dissatisfaction, and dissatisfaction is a kind of pain.
Every individual perceives things subjectively according to the given circumstances. And it seem that there are differing levels of intensity of desire (from just a low-level niggling feeling of dissatisfaction up to high-level stress, anger or hopelessness.)
There are some desires that when we know they will will soon be fulfilled, it is a pleasurable experience of anticipation. For example: feeling mildly hungry and arriving for Christmas, smelling the turkey just out of the oven, and the announcement for everyone to come sit down at the dining table.
When we desire something and believe we need it, but yet we don't know how to get it, that it when desire feels painful. (For example: feeling extremely hungry, arriving for Christmas, being told the the turkey just went into the oven, and noticing that there are no hors d'oeuvres).
I think as time goes on (and depending on circumstances) the sense of pain can shift to feel less painful, because we can learn to problem solve situations. (For example: remembering to always pack a small amount of food (nuts or protein bar) with you if you tend to have hypoglycemia episodes).