Fuel pressure issue

Hey there having a fuel pressure issue I get about 6 psi when I start up my motor, this is a carter mechanical pump on a 360 motor, now when I go out and drive I have sputtering issues I barely got home because it's starving for fuel, have s full gas tank and my pressure drops to zero and my fuel filter bubbles like crazy like the pump isn't pumping is it possible for the pump to have the diaphragm stick and not put out volume? I noticed when I run the motor at higher rpm it starves for fuel, and will hesitate cause it's not getting enough so my question is when the motor runs high rpm The pump will pump faster from the cam moving faster and kill my fuel pumping action is the pump shot? Also have checked lines for leaks etc it's not getting air cause I can suck fuel out of the tank with my mouth easily any help please