the flashbacks are mandatory for a ptsd diagnosis, I think.
But still: you can be traumatized by something that happened in your life and that is BAD no matter if it is labelled as PTSD or not.
my advise would be to go to a therapist that is higher qualified than just a bachelor's degree. In Germany you aren't even allowed to do therapy unless you do your master's...
PTSD is a really complicated diagnosis. I wouldn't sweat the DSM-IV classification part of it unless you're doing coding for insurance reimbursement. I do think it's important not to cloud mental health with slang (e.g. saying you have PTSD from an exam at school because it was simply challenging) but I think if past experiences that were emotionally or physically threatening are impairing the ability of someone to cope with / adjust to stresses and interactions in one's life in a debilitating way (including flashbacks), go ahead and claim it.
Oh, and the therapist's reaction to your complaining about your past making you feel guilty and needy? So wrong. I had what I think was a similar situation with more than one therapist - one said she didn't feel comfortable discussing my verbally and emotionally abusive relationship with my husband if he wasn't there to give his own point of view, so she could only talk to me about my own behavior. Huh?