I have forgotten how to write and think in sentances! AGRH I just cannot concentrate.

I can understand that. I feel like that too. It sometimes help to write down casual silly things that comes to your mind, things about what you don't mean to say about your research etc. After a while you find yourself writing again. I read that somewhere and tried it, it works sometimes.

agrh i give up - i cant get anything done. I am going home - theres no point in being in the lab if i cant concentrate. Ive had dinner and all i can think of is food. I dont know what is wrong with me.

yes, go home. It's a good idea. Is there any place that you can get some fruit from, on the way home? I hope you'll feel better tomorrow.