As I said in that other post, it sounds like agoraphobia. Of course I'm not a doctor, so I can't say for sure, but that's what it sounds like to me. Since you're already on meds for bipolar you must have a psychiatrist already? Call them right away and explain what is happening.
Depends whether you avoid social contact in general or just being outside. If you avoid all social engagements with people and don't speak to them on the phone, then yes part of depression certainly is not wanting to be with people. If its a fear of being outside or in enclosed places that would be a phobia. But only your psychiatrist would know for sure so it would be best to speak to them about it.