Find a new one. Find one that specializes in ADHD. You can absolutely be diagnosed as an adult, however the symptoms must have been present before the age of 12 or something, technically.
I had a doctor ask me if I had found jesus when first trying to get help w my issues. For real. It can take some time to find the right fit, but hopefully you can seek out an ADHD/neurodivergent focused therapist for better results
e: i was diagnosed by a psychologist/therapist. I have heard from several folks anecdotally that their psychiatrists are more detached and are mostly just there for prescriptions. YMMV
I haven't had cows milk in years. Somehow all my sauces and things are still turning out delicious! Lots of plant milk is flavored or sweetened. Buying regular/unsweetened almond or oat milk will work for most cases. I am extremely partial to oat milk and I would honestly drink a glass of it