My oil pressure was suddenly dropped or nothing and then pop right back up

I have a 99 Chevy Suburban and while I'm
driving down the road the world pressure
will be happy and then all the sudden it'll
drop down most the time it drops down
when I hit the brakes then it'll pop right back
up were supposed to run there for a little
while then will drop back down then pop
back up I don't know if it's the oil pump is
going bad or if it's just an electrical problem
with the gauges