I think you are so utterly and completely overwhelmed with "I can NOT handle this", that even if you had an escape hatch, you couldn't see it.

First, I recommend doing anything that can help you relax. Even a few simple very deep breaths will slow your heart rate for a few seconds. You have to calm a little.

And, you will see your therapist and tell him. Or give him a print out of this thread. It's important that he know how you feel. I love the idea of asking him to write something or give you something tangible to hold.

Stop saying how you can't. You can and you will. How could telling him your feelings be worse than where you are now, eh? Talk to him, it will help. Do it. Walk in the room and open your heart. It will not get worse.