You don't need your GP to give you a BP dx. You just need him to give you a referral to a pdoc, who will then give you a BP dx. Just go in there and tell him you want a referral to a psychiatrist because you want a proper psychiatric assessment and diagnosis. Most Gp's would not have enough experience or understanding to dx it anyway. My GP did actually dx my BP, but he has a specialisation in psychiatry. I then followed his dx up with confirmation by a pdoc.
You need a new GP too btw. He sounds like a jerk. You need a good team of medical professionals behind you to manage and treat your mental health issues.
Good luck, take care and keep us posted on your progress and any developments.