Seeking Advice on Getting Multiple Diagnoses

I've recently mentioned to my parents that I feel like I have much more difficulties than just Austim. When I was 15, I went to CAMHS, didn't diagnose me, but then I went again at 17, I got diagnosed with Autism. You can imagine the frustration I felt. After that diagnosis, I'm 20 now. I don't feel like that's the only thing wrong with me. I feel like I could possibly have learning disability, Inattentive ADHD, Bipolar, and Dyscalculia. So I mentioned it to my parents a few times, I've obviously feel like I have more than just autism. My mum's a therapist. So I told her this and she said I need to understand my autism first and to look more under the umbrella of autism. Both my parents said "I don't understand why you need to feel like you need to have a diagnosis, you already have autism and that you need to be diagnosed with this and this now, what difference does it make?" I literally was angry at that question. Like duh, I need to talk to someone and get assessed and to make an official diagnosis so I can understand myself better and others can too, because honestly it's worrying and exhausting everyday thinking what else is wrong with me and why doesn't anyone else understand me!?. Plus I don't really like self diagnosing myself either, because I could be saying I have this when I have something else or I might not. Can you please offer advice on what I should do?? Are my parents right??.