First of all I give you "made props" for opening yourself to feel all of these emotions for the greater good of your marriage! The majority of men could not even fathom having to courage to allow their wives to see other men.
I think you might be able to calm your negative feelings with a bit of work.
1. Tell your wife to please give you a second! A large chunk of the anxiety you have stems from the fact that they work together, and that you don't know WHEN they will have sex. If I were you, I would ask E if she could promise to not go any further until your tidal wave of jealousy has passed.
2. Maybe you need a different set of rules? Maybe no coworkers or close friends? Maybe just one night stands?
3. Read this article on how to get a grip on jealousy. http://www.cat-and-dragon.com/stef/P.../jealousy.html
4. BREATHE, meditate go for a swim or run.
Let us know how you are progressing.
Keep your head up you courageous young man!