Hi celtic, if you're really not feeling anything, just write down what not feeling anything feels like for you, if that makes sense??!!!.
For example a sense of detachment, a sense of emptiness, a sense of numbness, a sense of "I don't get how I should react", a sense of "Standing apart from things"................whatever's there.
I don't know if it will help returning to memories though, and trying to write down how you were feeling (even if that can only include physical feelings e.g. shaking??) as sometimes feelings can be buried real deep but still be effecting us/flicking that "I don't feel anything" switch". Watch for going "too deep" there though!! One step at a time.....
And of course, maybe "happy" memories might surface on reflection, reminding you to a point of what happiness actually feels like. Step towards recognizing/maybe feeling that again???? Possibly??????
But your feelings right now, are what they are, and I'd say that it will be really important to acknowledge however they are for you. Even if that's a "vacancy" there. That way your T is going to have a better understanding, and way to work forward with those feelings, what's gone on for you, what's going on for you.
Just a thought though, may not work, but.............maybe you could just "let yourself go" in some sort of art which may help with your expression of what you're feeling/not feeling???? Or maybe there's a song, any song, that resonates with you or explains it????
Alison