I'm so sorry you are having to face all of this right now. I know how it feels with school and all and feeling so overwhelmed and knowing you don't have time for a complete mental breakdown. I wish I had time to go escape form the world... even just for a little bit.

As for advice, probably my best is make a list, a list of things you have to resort to before cutting. Include time limits. Maybe first you have to journal for 10 min, then if you still feel the urge force yourself to attempt to study for a test for 10 min (even if you feel you can't focus), still feeling really bad squeeze an ice cube until it melts, then maybe clean one thing, then do one part of a writing assignment, then call a friend for at least 15 min... other ideas include coloring, praying (especially for others), doing small portions of work that needs to get done, hanging out with someone (I know that's not always available though), listen to a few songs, then maybe somemore homework; try to continue the list until you can either sleep or don't feel so desperate to cut and know you can make it through.

Also I would highly suggest you quit carrying that box cutter with you everywhere. It is not helping and it sounds like it is causing much worse damage than a razor which is just going to up your pain tolerance level faster (and I think we both know what that means.. more/harder...sorta working backwards). I could never ask youto not carry your razor blade with you.. not yet. I know I needed that for a long time, and even after I quit it took me 2 monthes I think before I got rid of all my blades. I've been cut free for 1 year 4mths and I still like to keep a safety pin with me (haven't used it, but its presence comforts me). I know you arn't feeling ready to give this up completely so I'm not going to ask you to, but really try to limit yourself (how often you cut, how much you cut, how deep they are, even how often you use the box cutter vs the razor... all of these are ways you can slowly ease things a bit), and when at all possible try to do the list thing I mentioned above or other forms of distraction.

Hang in there, you can get better, it's hard and scary, but at least it's possible (even if it doesn't always feel that way, try to trust me, it is possible).

(((((((((((((hugs)))))))))))))