why do you have bleed breaks constantly brakes parts were checked good no leaks

Your master cylinder is most likely the problem if the pedal intermittently goes away, 'without' fluid loss! Atually bleeding is not really helping, you just think so!

you are sucking air somewhere,poss the cailpers or rubber lines to cailpers. ck hyd lines for cracks also remove master cyl and look for leakage from the rear of cyl