hey, you should definitely bring it up, should tell your doc everything so you can get the best treatment

i dunno if bpd can be mistaken for adhd.. but you can have both
Borderline Personality Disorder Demystified - Symptoms of ADHD/ treatment in patients with borderline personality disorder.

maybe your records are still there, that would help, if not then might can get him to evaluate you for it..

do you want to drop out because you are having difficulty with the work?
or is it more related to the other people around you?