Therapist said diagnosis doesn't matter

I turn to the wisdom of the hive, since I am completely torn. Right now I am in rehab, after a nervous breakdown following complete overwhelm. I live in Germany and this is called psychosomatic rehabilitation and has nothing to do with substance abuse or such. Anyway, I was briefly diagnosed with BPD 10 years ago. therapy and medication (antiD) just took of the edge, never really helped. But I tried to endure, although anxiety grew... Now my son (12) is suspected to have adhd, so I did some reading on that and realized, that everything I learned about adhd applied to me. I dove into the topic of late diagnosed women and am now certain, that I suffer from ADHD and not BPD. today I asked my therapist about it and this is what he said \\- it's a fashion diagnosis \\- it had to be diagnosed around the age of 10 \\- he sees my bpd confirmed \\- BPD and ADHD is almost the same \\- it does not matter if it is bpd or ADHD especially the last one I think is highly unprofessional I don't know what to do now? shall I confront him? ask for a different therapist? I am only here for 5 weeks but don't have a therapist at home so I wanted to get clarity here... getting an ADHD diagnosis is very difficult in Germany - the wait-list is about 2 years long or one has to pay as much as one months rent. how shall I proceed?