I would suggest you do a couple of test before buying anything:
1. check your cable, sometimes you might damage it stepping on it with a chair or desk.
2. I find that squeezing the cable and puling firmly from one extreme to the other sometimes fixes internal problems in the cable(either way you will need to change it sooner or later but you will know it is not the monitor)
4.. ask someone to lend you another monitor and cable, try and make it the same input as your monitor (HDMI, DVI, VGA)
5. if even with a different monitor and cable you still have a problem then you might even have a problem with your graphics card... but it doesn't sound like that.