brake problems

driving to pick up my cuz for a church event and i notice my brake pedal almost seams to have air in the lines and the pedal is lower then I am used to. So I pick him up and check my fluid. It is pretty low. I hit up ol wally world and buy a big bottle and bleed the brakes in the lot (done this many many many times so I know what air in the lines looks like) I notice there are no visual leaks. My jeep is still covered in a dried bright colored mud so any water/oil shows immediately and everything around my calipers and drums is dry. So I top it off after tryign to bleed them (no air came out) and notice no change in the pedal. I drop off my cuz after the event and on the way home try to feel out the pedal (I didn't want to test it with him in the jeep) so I was on an empty backroad and I pushed the pedal down. It goes to just about the floor and the brake light flashed briefly. But then you can pump up the brakes and they work fine for a while which to me feels liek air in the lines. Is my booster or master cylinder shitting the bed? I'm uneasy about this and need to find out what's wrong, I don't have a back up vehicle at the moment.


specs:
90, 4.0, auto
recently put new pads on, compressed the calipers back in if it helps diagnose it
thanks for your help

sounds to me like you need to adjust your drums.

drums hold fine (ebrake still works too)

drums need adjustment, or rear brake cylinder leak, or master cylinder is going bad.