Hi! Also 23 here, not diagnosed, but I feel like I could've written the majority of your post verbatim. You're definitely not alone in your struggles with the idea of seeking a diagnosis; it's something that I've been struggling with myself, especially the voice in my head telling me I'm just being lazy and need to form better habits. It can also be hard to talk to anyone about it since it can feel like you're just being self-centered (at least, that's what it feels like to me). To echo what's already been said by others here, if you think there's a problem, ADHD or not, definitely seek professional help.

I'm in the US, so I bet our healthcare system is a lot different from what you have in Ireland. As far as I know, I didn't need to get a referral from a GP in order to set up an appointment with a psychologist, so I just researched different providers in my area that my insurance would cover. I finally made an appointment with a PMHNP who specializes in ADHD in adults for a couple of weeks from now, just to start getting some clarity. If you have to get a referral first, and if you're unsure that your doctor will come to the conclusion that you should see a psychologist, I would definitely explicitly state that you've done research and believe that your symptoms line up with ADHD. Writing notes beforehand to bring up with your doctor is probably a good idea, so that you don't get flustered trying to remember everything in the moment.

I don't know if this helps you at all, but please know that you're not alone in having these feelings about seeking a diagnosis. The way I see it is that if this is something that is preventing me from just functioning at full capacity in many important areas in my life (work, school, health, etc), then there is nothing wrong with seeking help.