Ask him to open up your marriage so that you both can have your cake and eat it too. He can have his "marital" status and you can stay within your codependent existance with him and get your sex on outside of the marriage. What? No?
Well if the answer to that is no then nothing short of marital councelling with a psychologist or a minister if you belong to some organized religious cult *coughs* organization will help the two of you. " I really do get absolutely nothing in return. This is three years, I'm at my wit's end" is enough motivation to do either of the two options above.
BTW: If you've not had sex since you've been married I do believe you can get the farce of a marriage you're in annulled.
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion