Re: Think that my partner may have Borderline Perosonality Disorder
It would be impossible to diagnose anyone without his cooperation, and with a doctor trained to make such a diagnosis. There are many types of mental disorders that can often even overlap, making the proper diagnosis somethimes quite difficult.
the fact that he has been medicating himself with a prescription that was given to his mother is unacceptable, and could be dangerous. Each of these medications have very specific uses, and trying to treat himself with an antidepressant could have terrible consequences, and actually make what ever issues he does have much worse.
The thing that would bother me the most, is his ability to lash out at you, and seem to be unaware of the hurt his outburst are having. As much as you love someone, they must love themselves enough to seek out the proper medical help when it is needed. This takes self acceptance, and the desire to help himself. Without that, there is hardly a thing you can do that will ease these issues.
My best advice would be to have a very frank and open conversation with him about how his behavior is affecting your relationship and ask him to seek the proper help. From there you can be understanding and support his decision to go through with treatment, but that can be a long term thing, and can have many ups and downs. If he is unwilling to take a hard look at himself, then I would move on.
So many people are living wonderful and productive lives with many types of mental illness, and there have never been more understanding and treatments available as there are today. On the other hand, there are also very many individuals who's lives are torn apart due to undiagnosed illnesses that are left in denial or refusal to accept and treat,for those people, relationships and life itself can be a long and difficult path. I would try to encourage him to stop using the antidepressants that are his mothers as soon as possible.