Well it's always good to get it out. Anyone would be nervous for an upcoming biopsy, but especially someone who suffers from anxiety. I imagine it's ten times worse and eating and not sleeping is the side affects, among others. Just try not to judge yourself to harshly, it is a very stressful time in your life at present.
I know you know and understand all the cliché sayings about taking one day at time, etc, but just know that we are here for you and you are welcome to let your feelings out at any time this weekend and afterwards if needed. That goes for all of us too!
I hope you can get through this weekend and not totally go nuts with anxiety and stress... just try to distract yourself as much as you can (hopefully not always with food).
I know I am thinking of you and I hope everything goes successfully on Monday. I'm sure the anticipation is way worse than the procedure itself, and I know that knowing that fact doesn't necessarily help with the anxiety, but keep it in mind. Things could be worse, right?
Wish you luck!