Strictly speaking, the phrase "Jealous Much?", means "are you very jealous?", that is to say it is question rather than a statement.

By contrast, it can be turned into a statement simply by reversing the order of words. Thus "much jealous" would mean "I am very jealous".

Unfortunately, most people today have a flagrant disregard for proper syntax, and so the distinction between the two has become blurred.

However, the literature on the subject is very unambigous on the matter, and most experts consider the word order to be so important that both question marks in written work, and intonation in speech are irrelevant. That is to say, the question mark may be freely omitted from "Jealous much?" without affecting the meaning, while any stray question marks in "¿Much jealous?"are to be ignored.