No desire at all to touch my girlfriend sexually anymore? how can I make sex interesting again?

she's definitely gonna feel unattractive or like you don't want her. i would start to feel down about myself. what's happening to you is common for guys under a lot of stress. tell her that so that she is educated about it (if she doesn't already know). you need to start getting more sleep and i'm sure you will be able to get more sexual if you can relax more. or maybe you can see if you guys can go on a little break and get back together when your stressful school situation is done. but make sure she knows this is the only reason and you want to get back together when you're out of the stressful situation...good luck..