I can absolutely relate to this. I am the exact same way. I really, really want to email because I feel like I'm going to burst if I don't, but then I feel guilty and am terrified that she is going to be angry at me. And waiting for a response is the worst.

Have you talked to him about your fear? One of the things that my therapist does now that I really appreciate is that she will email me a very short response saying something like "Thank you for the email, I'm looking forward to talking with you about it next week." It takes her maybe 5 minutes and saves me days of agony. But even though this anxiety seems to be very, very common with clients, I'm not sure all therapists get it.