HELP!! Problems with my A/C!

I have a Cavalier but I'm having problems with the A/C. It does blow cold air but it goes on & off every 2-3 seconds. I had the fan and water pump replaced, fuse checked, etc.. Would anyone be able to help?

AC charge is either too low or there's too much oil in the charge.
(Too much oil will make the compressor reeds "sing", though, so it's prolly just low.)