The cruise stopped working on 2003 GMC Sierra. Is there a fuse and where is it

Sounds to me like your brake light switch (located towards the top of your brake pedal). Check and see if any brake lights are out first. If they are, replace the bulbs first and see if the problem is fixed. If not, I'd go for the brake pedal switch. Its about a $30 part. It either needs to be adjusted (as in, your brake lights are coming on while driving) or it needs to be replace.