My struggling and almost dead christmas cactus grew a lot of new leaves and now they are dropping off?

I've had problems with mine but it's getting better. Don't water it too much and keep it out of direct sunlight. When it starts growing the new buds you know you're doing it right. If they drop off put them bottom down in the dirt around the original plant.

You may be giving too much water, being a cactus it doesn't take much. I know that in order to have flowers, it needs total darkness for the months leading up to Christmas and that includes artificial light.

most people think their giving the plants to little water when its mostly to much

This can help.