Maybe one solution would be to resolve that from this day forward, you will tell your T if you are having suicidal thoughts or behaviors. What's past is past, and if your fear he will be angry because he wasn't fully in the loop before is a stumbling block toward disclosure of past events, just start today.

I have told my T a number of things from the past that he asked me why I didn't tell him earlier. Sometimes, my answer was because of trust or shame. My T did not react poorly or judgmentally. He acknowledged that it takes time to develop a relationship where one can tell another person the hard things.

Do you think if you had sui thoughts/actions again, that you would be able to tell your T about it now? If you don't have enough trust for that, I think that is something to share with T, so at least he knows you need more trust between the two of you. (He may not know there is anything wrong on the trust front.) And maybe he can help you develop greater trust in him...