The oil presser gauge keeps going to 0 when i stop but when I give it gas it goes to about 40. what do you think the problem is

Either you have a bad oil sending unit, which is the thing that measures the oil pressure, or you have low oil pressure, which means you have a bad oil pump, cam bearings, crank bearings or a combination of all three.

I think your sending unit which sends a signal to the gauge needs replaced. Oil could be sludgy and gumming up inside the unit. But basically you could drive it for awhile but I suggest you get it in for servicing unless you want to try to fix it yourself. One quart low of oil could also do this. How many miles do you have on it?