I hope you got some sleep last night and can function better at work today. I've found that when I can't sleep, I put on some guided meditation. You can find a lot on youtube. I usually do ones for pain, but you can pick whatever kind you want. Most concentrate on deep breathing.

Hopefully you and your friend will have a fun time this evening. idk if you should tell him about your illness, depends on how well you know him and all.

Good Luck!