Why, no matter how hard I try to avoid it, am I an emotional wreck?

Seems like you are a person who has a lot of self awareness and maybe sometimes even your self awareness is too high. There is a lot on your mind and you're flooded with emotions. It is really understandable (maybe even wise) that you prefer not to share your distress with your family -seems like they cannot contain all that very well. I think it would be recommended to keep going to the therapist and also find some additional support sources like good friends, online support places (like mycontainer.org) and maybe writing and blogging as a way to express your emotions.