why am i putting 1 to 2 gallons of antifreeze in my truck every week?

Because it's low? Sorry, lame sacrasm. Do you see pudddles on the ground? Is it in the crankcase? If no and no, head gasket, water jacket to combustion chamber and out.

DavidH25 has the right idea. Also while the truck is running outside in the open air. Have someone sit in the truck to turn it on & off & look underneath to see where it is leaking. It may not leak until the engine is hot. Good Luck.

why are you putting 1 to 2 gallons of anti freeze in your truck a week? I don't know, seems like an expensive habit....does the truck run hot, has it ever had heating complications? when the truck is cold/cool open the coolant reservoir, do you smell exhaust fumes, or coolant? or both? or gasoline? open the oil cap, what do you smell, burnt oil, or ??? check your oil, what color/texture is the liquid, milky/white, black, runny??? david had a good idea for checking the coolant leaks...either when you park it for the night/day (for best results), a piece of cardboard, and a layer of kitty litter on top of it, and let it sit, look for a path of where it may have ran along hoses or lines that is alot of coolant, so a leak should be easy to find...look at the exhaust, what color is the tip....pull the carpet and insulation off of the passenger side floor, way near the dash floor meet, metal floor, is it dry??? let us know what you find with all of these questions, and we shall tell you why ....