I read your post, and felt indentified. I hope I can offer you some words of advice and comfort. I am also a very outgoing and friendly person, and for many years I felt that I had a problem. There is no shame in shitting alone, and the measures we take to feel confortable to poop. One thing I can tell you for sure is that the more I thought about it the worse I felt. Relief only came with acceptance and pride, I still shit in private, but I dont feel guilty or anxious about it. The only thing that makes you anti social, is your attitude towars society, and at the end of the day who isnt antisocial at some point?
One thing I can advice is, Choose to poop where you want and when you want, the people around will understand. and the person that loves you will support you 100%.