Or were you? I hear people say something like that fairly frequently, mostly being funny. Often, though, what they intend when they say “jealous” is actually a different feeling.
Originally “jealousy” and being “jealous of” someone expressed a fear of either losing somebody’s affection, or of being replaced by another, whether in love or in some other situation. Its meaning expanded to include guarding something vigilantly, rather like hoarding, out of a desire to maintain your favored status with a person or object. A jealous person can possess and vigorously guard a person, such as a lover or spouse, or a thing, and they passionately want nobody to take what they regard as theirs alone. In extreme cases, jealousy, i.e. this fearful, angry resentment, arises if somebody even compliments the jealous man on his possession.
Given the intensity of the emotion involved, it’s not surprising that “jealous” derives from the same Latin word that gives us “zealous”, “zeal”, and “zealot”. The Vulgar Latin word “zēlōsus” is our direct source in English for “zealous” and “zeal”. Late Latin “zēlus” is the source of the Vulgar word and of the Old French word “gelos”, which is the source in English of “jealous”.
Then there’s “envy”. Distinct from “jealousy”, the emotion in “envy” is a feeling of discontentment, resentment, even a pained desire for the possessions or qualities of somebody else.
In other words, you can be envious of somebody’s good looks, their wealth, or their lover, but in the original sense of the word, you could not be jealous of them. You could only be jealous of your own wealth, your own good looks, or your own lover; you guard them as yours and yours alone and you do not wish to share them.
Over time, though, people lost track of which word meant exactly what, and “jealous” edged out “envious” as the favored word to describe both types of resentment. Most modern dictionaries acknowledge that “jealousy” is synonymous with “envy”, so the originally clear difference must have gotten confused some time ago.
It’s a good distinction, though, and one to keep in mind especially if you’re reading an older piece of literature where the author may be consciously specifying one emotion over the other.