birdcage instaed of ribcage. Is the bird where your heart would be?
Does it flutter like a heart? This would be supported by this.
Dream Moods: Your Dream Symbol Interpretation
Perhaps you're feeling like you can't let go of you heart/love/free spirit for some reason? Would it leave you vulnurable to pain? is a person/people pushing you or demanding that you open up more or something like this?
anyway just some things off the top of my head. maybe relevant maybe not. anyway hope you work it out, doesn't sound too pleasant.