Hi Rosalie and thanks for choosing Just Answer. My name is XXXXX XXXXX I will be happy to assist you.
It sounds like your monitor may have gone bad. Please try the following first:
If that doesn't fix it, can you please tell me if this is a flat screen (LCD) or old tube style (CRT)? If you can get it, the model number would be helpful. Thanks!
OK you can try doing a reset on it (generic instructions are below).
If that doesn't work, then the monitor will need to be replaced. The good news is that flat screens are fairly inexpensive nowadays, like this: