I think the most important thing for you to do is to work on your feelings about the situation and your response to it.

The reason I say this is that you say that you are feeling very stressed and physically ill. NOTHING at work is worth that! And your anger is probably getting in the way of effective problem solving.

In a nutshell, don't focus on the unfairness of the situation. Don't focus on what your co-worker or your boss 'should' be doing. You probably can't control either, and you will waste a lot of energy and build a lot of stress in thinking about it.

Instead, focus on doing your job well, and getting as much enjoyment out of your work and your job as you can. Or focus your energies on putting together a knockout resume and finding another job. In other words, focus on those areas that you can control, where you can be effective. If you take positive steps in your own behalf, you will be less overwhelmed.

You may decide - when you feel less stressed - that you want to talk with your co-worker or your boss, and that you feel able to do so with less anger and more rationality. Or your may find out more information about the situation that may lead you to decide that you are glad you didn't blow up.

Good luck. I know it isn't easy!

FurPaw