antifreeze is almost gone

its a 2wd 4.3 vortex hope its not a blown head gasket im not sure.truck runs and drives nice.we lost heat so i checked antifreeze and its way low.we just did a flush and fill and new thermostat about a month ago.39000 original miles

It might not be leaking at all since you just had some work done on it. There might have been air still in the system when they handed it back to you as done. Every time I do work on the system, I make sure the coolant bottle is completely filled when I finish because I know that when the engine cools, the vacuum will start pulling coolant back into the radiator/block.

i filled up radiator and overflow.drove truck 20 min or so.leek on ground under or somewhat under drivers seat.things looked wet and it was dex cool on the ground i see a drain hose in the area and hoses to radiator high pressure maybe noticed that radiator cap after that drive wasn't even hot Luke warm lower radiator hose upper hose not to warm either but up here in Vermont it was 25 ish.so confused over this 4.3 vortex 40000 miles on this truck.seems like allot of moisture out tailpipe to.hope it is not head gasket ect .thanks for any help with info on this .Tim

I have a block that has less than 40,000 miles on it and i will let it go cheap,i have no use for it after husband left me