side chick

So, this just happened and I'm so sad, angry and confused. I've been with this guy for ten years and today, everything just blew up. I got out of my relaxing shower and checked my phone and saw a girl had been blowing up my Facebook messages. She said she was told by a friend of mine that I was sleeping with her boyfriend. She told me to send pics of my text messages with him and proof he was cheating, I didn't. Then, I got a call from the guy we both happened to be dating saying that it was all my fault for this drama and I shouldn't have run my mouth to people about us. Then he said if I cared or respected him, I had to delete all of our messages, his pics, everything from my phone. And then he said he no longer wants to see me. I'm so hurt and confused. I don't know if I should send the girl all the pics and messages as revenge and ruin him, even though I'm sure he'll just make up shit about it and he'll stay with her, or if I should just delete everything. I hate him so much right now, but I still love him too. What should I do?
UPDATE: so I did send her everything. She ended things with him. He called me saying I was dead to him and he hurts people who hurt him and I will wish I never did what I did. He said he's going to fix things with her and I should know not to fuck with people who know where I sleep or where my family sleeps. He has a key to my house. Said I need to relocate or I'll regret it. All the nudes shown to his other girl is now going to be uploaded somewhere and it's going to ruin my career. I'm a nanny. I can't have that floating around. Now I'm so scared. I threatened to call the police on him and he told me to go ahead, they can't do anything until he did something to me. I recorded the whole conversation, but now I'm just very scared. I don't even know the guy anymore the way he's treating me now.
UPDATE #2: everyone is asking how do I know I'm the side chick, is because I'm. Or the attached sort of girlfriend. I liked my space. We lived in separate homes. He just had a key to mine. We both supposedly worked long hours and he had class after work. I trusted blindly, but the other girl let me know there were two more girls he dated along with me some years ago. I guess I was the main in a way, but for the fact he'd rather be with the other female made it feel like I was the side one this whole time.
UPDATE #3: I got a message on my phone this morning of him apologizing and begging for me back. I guess he couldn't fix it with the other girl. But New Year, new me.