1991 Chevy Blazer Unknown car problem

Noises problem
1991 Chevy Blazer 6 cyl Four Wheel Drive Automatic

My Blazer's oil pressure gage started dropping but when I would accelerate it would rise to normal and when I dont accelerate it drops, My Blazer runs fine though and starts fine but now when I turn the ignition on there's a sqeaking noise coming from my drivers side right around the washer fluid container and the oil pressure gage is all the way down. Whats wrong with my Blazer!