How long...

Has this been going on?  Found out some news today that has rocked me to my core.  What do you do when someone you're lived with and loved for so long commits the ultimate betrayal?  How do you restore trust?  How do you go on?  How do you pick up the pieces?  How can I NOT feel like I was the second choice at this point?  She chose someone else, and he chose me, but as soon as he and I were exclusively dating she changed her mind.  Kissed him while he was engaged to me.  And tonight, while I am in Phoenix on the eve of my sister's wedding, he is on a date.  With her.  And, two of the kids know.  How does this help them with their multiple issues?  And when he's texting me saying he's sorry, is he texting her and promising he'll leave me?  He has told her he loves her.  And has told me he is IN love with me.  The line has still been crossed.  It is adultery in my mind.  I am heartbroken.  He is the love of my life.  There have been some problems.  But I've always loved him.  And now I am lost.  Lord help us...