I find change triggers me as well. As for your psychologist and the DBT group. Can you change groups some how? Can you get up enough courage to talk to this person.
DBT is so important for people struggling with BP that I'd hate to see you not get anything out of it now, because of the change.

As for your boyfriend, you are lucky to find such a young man that is willing to be so supportive. Don't feel selfish, this is just all part of your symptoms, I would imagine