I think you should tell your T exactly what you posted here. Also, she allows out of session contact, right? If so, might be helpful to send her an e-mail while you're home and freaked out after an appointment, just to get the immediacy of those thoughts out, so she can see how you're feeling. Or even just type it out and show her during your next session. I'll often have insights while driving home that I sometimes e-mail my T about.

I have similar experiences sometimes, particularly with marriage counseling, where I can be OK in there and think, "Hey I didn't even get emotional," then get in the car and start sobbing. I used to be that way more with T, but now I just go ahead and cry or freak out there in front of her. I'm not sure when that shift happened--maybe I got really upset in there one time, and she accepted it and helped me through it, so I saw it was OK? (I do cry sometimes in MC and actually had a panic attack in there recently, which was something that hadn't happened in there before, though it had with T.)

So definitely tell your T. Maybe something you can work on is trying to experience your emotions while you're in there rather than suppressing them until you're alone. It's not easy...I grew up with a message from my parents to hide my negative emotions (sadness, anger, etc.), so it's been difficult to learn to let those out. But it's definitely helped.