I get like that. I envy happiness in others. I'm jealous they can "feel" happiness. There is a disorder linked to predominant feeling of this nature. I read about it on this website somewhere. I'll post again, if I can find it. I'm not saying it applies to you, but I know it does to me. It did help me become awareness of this feeling & how it applies to me & my mental issues. You are not alone in this. Being aware of it, did help me put it into some sort of perspective for me. *big warm hug*
~Nutty buddy