What is it like to be a mistress? Is it worth ruining a family?

I'm 23 years old, I have been in a relationship with a guy for almost 3 months. It's been great so far, he cherishes me and he is very emphatic so it's lovely to have a deep conversation with him. However, he told me last week he's married and has 3 kids. I was flabbergasted and didn't even know what to say to him, and even though I was upset I didn't say anything to him because I was traumatized due to the shock. And that was the whole conversation and we didn't speak anything else.<br><br>Over the weekend he came to my apartment and asked me to say something, he said he didn't know what to do and that he loved me and that he already imagined having kids with me and he didn't know if he was excited about his future. He told me he was sorry for ruining my life and that he'd never regret cherishing me and showing me lovely things because he'd never regret it.<br><br>He also mentioned that he loved his wife but wasn't in love with her, and that he didn't love her as much as he loved me. He asked me if we could continue our relationship but I told him I wasn't sure so he said I should take my time to think about it. I told him I wanted to see his family and he told me no, that he'd never do that because it wouldn't be fare to his wife and kids. I told him I didn't care about being hurt and I wanted to know the damage I had caused. He just vetoed it and told me "you don't want to see it. Trust me."<br><br>I have been trying to get over it for the last two days but I'm still heartbroken. I don't know what to do, I've never been in this situation and I don't know how to proceed. I don't want to be the girl responsible for breaking a family but at the same time I don't want to let him go, because I fell in love with him. I don't know if I have to feel guilty and I don't know what to do.<br><br>What is it like to be a mistress? Is it worth it?