How to get a mental health diagnosis UK

How do I go about getting a diagnosis? I know that something is wrong with me but I don’t know what. Obviously I have ideas from googling symptoms but nothing exact. How do I go about getting a diagnosis through NHS?

For me I had to go to various other lvl2 therapy before I could apply for CAMHS. I had to see the private equivalent of CAMHS last March and got referred to a six-week therapy course with no diagnosis, and when that didn't work, I got moved onto lvl3 therapy and had to go to CAMHS. I have no diagnosis still, but I think they're trying to get me one. Pre-warning though - especially at the moment, CAMHS are SERIOUSLY picky on who can come to them, I wasn't ever going to go until the school and my previous therapist pushed for it, then they weren't very happy when they saw me. It's hard to get a place in CAMHS, you have to try in various other therapy before they notice your existence, or you have to be referred. Sorry this doesn't help, but the sooner you start with lvl2 therapy, the sooner you know whether you'll have a diagnosis or not.