J.G.
I haven't been there and would never want to presume to know how tough this is. I do believe you are an incredibly strong person for having placed your child with a good home. I really want you to know that I really commend you for doing that!
Then only thing I can offer is simply a reminder that kids at that age often say incredibly hurtful things, that they don't really mean, because they are upset. He probably doesn't mean it and doesn't fully realize how much he's hurt you. Kind of like when I use to yell at my mom and say, "You don't love me." I knew she loved me. I was just upset and wanted to get her attention and show her how mad I was. Never in a million year did I want to hurt her as much as I probably did.
I'm sure your son didn't really want to hurt you that much. He's just a kid. Just keep loving him and answering his questions honestly. I think you're both doing great!