When DS was going through that, I would put one problem at a time on the whiteboard. First we would walk through one with me explaining and drawing visuals, then the next one he would tell me how to solve it, I would write out what he was saying, and then he would have to copy it down on to his page. Separating each one away from the sheet helped lessen his anxiety.
Now he can do a whole page without the whiteboard. We reserve the whiteboard for the really hard ones - easier to erase.
(Edited for spelling error. Oops.)