I can totally relate to what you're feeling....
2 sessions ago, I brought some serious past SA to the surface...and I was filled with anxiety for days afterwards. During my last session, I tried to bring it up - but couldn't - and afterwards I felt awful because I felt like I wasted the session tip-toeing around what I really needed to address.
I hope you feel better soon. Get a good night's rest, drink plenty of fluids...and hopefully you'll be able to make it to your appt....