I do not think it is possible to "have" to tell your T anything. You have to do it when you feel ready. T's can be pushy when they think that telling them something will help you...and it probably will help you, but it won't unless you feel ready to do so.
Just remember that this might not get easier to talk about and that progress can be difficult to make without working through these issues.

Wishing you the best,
Jessica