For some people the sense of fellowship is more important than self-being. If you are one of those, well, it's going to be tough for you. Anyhow I would recommend:

1. Take little walks during work. 2. You also need a sound board, a colleague whom you can trust to validate your work and thoughts, because the one thing you can't afford is to redo things. Just trust this random stranger from the internet on this one. 3. Try to get a fix on the date when you can take a time off.Knowing that takes of the edge off a bit.