I can relate. This used to happen to me at work too. It was awful. I would either be up or very down, and never an in between.
I do have a comeback....Not sure if it would apply.....You could say...."Why don't you join me in being happy. You
might like it!" And, see what they would say......because they won't know how to take that comment- sarcastic, synical, nice, complimentary, etc....it is all in how you say it and in your body language in presenting it.
Simply- Just be you and don't feel ashamed of who you are because when a person starts to do that, then one begins to feel worse about themselves; right? Why try to be someone you aren't?
Maybe those around you are unhappy and jealous too. Even though you have a condition that can cause this to happen, they are probably envious of your personality. And, if that is the case, it is their problem. Be proud, stand proud, and live proud.
Take care and hang in there!!!! Live, love, and laugh hard!!!!!!!!