Like several others have already posted, my advice is to wean yourself off coffee slowly.
Cut down the 2 jumbos + tea every day to just 1 jumbo, 1 large, 1 tea. Do that for several days. Then cut down to 1 jumbo, 1 medium, 1 tea for several days. Then cut down to 1 large, 1 medium, 1 tea for several days, etc.
My favorite non-caffeine substitute is called Caf-Lib. I don't know if you have that in your area. It's sold in the coffee section of my grocery store. Just add hot water and stir.