I did it. I looked at her phone. I betrayed her trust and I crossed boundaries. I have never been more disgusted with myself.

I have been a bit (yea right, "a bit") insecure about her ex by the way she mentions him and that they're still not divorced. I'm not the other guy, they're in the process of it.

She went to the bathroom recently and I held her phone in my hand. I stared at the phone and made sure to touch my index finger every 3 or 4 seconds so it wouldn't lock. Fuck me.

I did this for about 4 minutes. Finally I mustered up some [cowardly] energy and read texts between her and her ex. It was exactly what I knew: She's over him and he's pursuing.

This was about a week ago. I've slept maybe 15 hours since then and it's been hard for me to look in the mirror. The worst part is our sex life is the best I've ever had, and frequent (7-10 times a week), and yet I can't perform (since I checked her phone). She's asked a lot of questions about what is wrong, because I've been clearly distant (she knows when I am), and I have yet to fess up.

I've never felt this way about anyone. We're so open and honest about everything: fears, relationships, sexual history, everything. She deserves to know about what I did, but I'm not quite sure how to put it.

How would you want [clearly a terrible word] to receive your partner telling you they snooped?

EDIT: I know I was wrong. Please refrain from reminding me.

TLDR: I snooped for insecure reasons and she needs to know. How should I tell her?