There is no possible way on this planet I could go to a all in in Mexico and not drink. I sort of think of them as a place to drink in the sun. One thought would be to cancel it and rebook another vacation, even in the same area where you at least have to pay for the liquor. It might be enough of a barrier to give you a chance to not drink.
We stopped going to all ins because all we did was hit it from breakfast till 2 then nap til 5 and then dinner till dark. It would take three days to feel normal after 10 days in the resort.
Just my opinion. But if you booked at another place where they did not have everything all in it is usually quite a bit cheaper, but then you don't get all that lovely food. Nothing like hitting the sushi bars and getting full!!
Good luck.