Trying to open up to my SO about my past!

I just cant... I dont even have the words to explain it i know what happened and everything but this situation still weighs heavy on my heart tbh i don't ever really see it "going away" but how do i try to tell him? He wants to know about it but idk how should i tell him? *PLEASE NO JUDGMENT OR RUDE COMMENTS* Thanks *oh i have tried to tell him but i just start to cry about it*