It sounds like this is a very important relationship you have with "Buddy" and that you're proposing a big change. That's bound to be rocky for you and for Buddy as well--whether or not he's interested in you romantically. Unless he thought you were joking (is that a possibility?) my guess is that Buddy's reaction to your declaration of love was mostly shock. Your long history as friends might make it especially surprising for him.

No, you did nothing "wrong." But I would suggest that you think about where you'd like your relationship with Buddy to go now before talking to him again. Are you ready for a rejection? What if he says he's in love with you too? Are you ready for that? And can you handle the possibility that all this might destroy your friendship?

Maybe consider how you'll feel about the possible outcomes, and if you think you're prepared, invite him to have a quiet conversation with you and then bring it up again. Hopefully he'll want to tell you how he feels--even if you decide (by yourself or together) that you'd rather stay friends than try to get romantic.

Especially after the hard times you've been through, I suggest taking it all pretty slowly and trying to be flexible about your relationship with this valuable friend.