How did you find the strength to leave?

I have been with my husband for 15 years and I can honestly say from the moment I met him he was the one. I have never wanted anyone else, I have always felt so content with him, just being near him makes me happy, I can’t wait for him to get home from work. Together we have the most amazing kids, my husband treats me well, is kind and caring, looks after me when I’m sick, I have no doubts that he loves me. Then a bomb went off, last June he showed me a false eyelash stuck to a t shirt that he thought was mine, news flash it wasn’t. This of course set off alarm bells, when I had an opportunity I went through his phone and found messages that he had sent to escorts, no appointments were actually booked but he had been enquiring. When I confronted him he claimed that he was enquiring for a friend who is very awkward with women and still a virgin at 30+. I was devastated, i literally felt like I wanted to die. I could not bear the thought of not being with him and even worse telling our children daddy is leaving. I can’t say I let it go, because it frequently comes up, I obviously do not trust him, his story has never changed. Now we are here, I asked him for something and he told me to get it out of his coat pocket, inside a pack of opened condoms. This is his story earlier in the day he was involved in a car accident, he dropped his car at a mechanic who lives near a halfway house and he was emptying thing from his car which is a complete mess he was dropping things and picking them up just shoving them into his bags/pockets. The pack of condoms was water damaged as though it had been soaked over a long period. Now again I am in the same position. Please tell me how do you find the strength to walk away from someone it feels like you would die if you were not with them? How do you break your children’s hearts? Ladies how do you find the strength to stop allowing a man to disrespect you over and over again. I am completely shattered.