I can't speak for ADHD but I think it's quite alright to self-diagnose for depression and anxiety. I've been through the diagnosis prosses for those multiple times and it's exactly the same as taking a "do I have depression?" quiz online lol. If you want to chat about symptoms, treatment, diagnosis, whatever, you can message me any time :)

Hi! Self-diagnosis for anxiety and depression is usually ok. As for ADHD, it is good to get diagnosed by a professional. Your doctor will be able to point you in the right direction to go through the process of getting diagnosed. Before you go through that process, I recommend writing down anything and everything that you experience that you think might be related so that you can talk about it with the people doing the diagnosis.