You apparently have signed, at least in your mind, an agreement to eternal servitude without recompense. You do it all and your wife does nothing. I think you have it right when you say she has gotten spoiled. All things are subject to revision and resission - pick a time to set aside to talk about what you are feeling and your sense of having an overwhelming share of responsibilities. If she is reasonable she will acknowledge she had it good but now its time to pick up some of the responsibility herself. If she denies that you do I would take unilateral actions to change it myself. Do what you feel you can and what you want to. STOP SCRATCHING HER DAMN BACK, that is in no way an essential maintenance item and if she's not helping out she has no right to expect you to continue. DO NOT BE A DOORMAT, you appear to have conditioned yourself to it although it is getting uncomfortable but you are too defensive, it seems to me, by your own words seemingly reluctant to make a change and feeling you need to justify your desire for a change when it seems only common sense and courtesy to me.

You need to disavow her asap of her mistaken belief you are her hand puppet houseboy. Try to communicate maybe she will cooperate, if not, then there is no need to compromise - it takes two - do as you please. Take back you life. My father did much the same for my mother but it didn't stop her from leaving him - none of his acts of love kept her with him. My father didn't know how to talk about love, he was born in 1895 to an immigrant farmstead with 14 hungry mouths and there was no time for such things. So his way was, like yours, to do nice things however when the person you are doing them forces ceases to be grateful and sees them as an entitlement its time to set the damn record straight.