Diagnoses are for the psychiatrists and therapists, to help orient them with what issues you appear to have and how to go about treating them. If you go to see them, you have a "problem" (or you wouldn't go to see them) and they are going to try to put your difficulties in their orientation.

You may/may not have multiple, overlapping difficulties and so, who you go to see if going to treat you in their orientation; a psychiatrist is a medical doctor and is going to see what medicines might help, an educational psychologist might look for learning disabilities or difficulties and treat them, a psychotherapist will try talk therapy, a social worker might focus more on your relationships, your interactions (social :-) with others.

There is no "right" diagnosis, it is who and what appears to help you learn to live your life better and/or deal with your problems. For me, it was better to concentrate on my T and what we were doing together, if it was helping me, rather than a diagnosis or what the T was doing as a T, etc.

I feel there are only so many "broad" illnesses; if you are depressed and anxious; you have to decide, which is worse and work on that one first? People are not simple so they do not have simple problems that fit neatly into a diagnoses but someone working with us has to start somewhere so they look to see if you are depressed or anxious or both or could be bipolar or have a personality disorder, etc. and then, as they work with you more, get to know you better, they can perhaps get a better idea of more specifics.

I differentiate medical illnesses as not being primarily about "living" your life like mental illnesses are. Yes, my medical illnesses influence how I live my life but not the bare bones living of it. If I have a broken leg, I get a cast and hobble around for awhile and it's a pain in the butt but not about my "life" per se. If I have depression, anxiety, or a mental illness though, my thinking/feeling is affected and that influences how I live my life. There's a huge range of overlap but my symptoms are pretty much going to help me decide if I want to look at medical or mental, see my primary care physician or my psychiatrist first?