I see it like women finding a lump in their breast or a man feeling a testicular lump or roughness. It may be nothing, but if it IS, it’s better to get it checked out and get peace of mind that it’s nothing, or, if it IS something, to be able to get treatment as soon as possible.
You have described quite a few symptoms of ADHD, and feel that you’re struggling to deal with it in daily life, as well as at an emotional level. It’s just my opinion, but I recommend you get it checked out and if necessary get a diagnosis so you can get help. And if a medical expert says you have an illness, maybe your father would be more accepting of it, since it’s not some ‘other thing’, but his own son being diagnosed by a medical expert. I know it can be scary to go for a diagnosis. I was almost afraid when I went to my doctor, worried that ‘maybe there’s nothing wrong with me, and I just suck and am lazy’… I suspect most of us think that way at some point before getting a diagnosis. But either way, it’s better to know, to have the knowledge of what’s going on.
And feel free to use the cancer check as an example of why it’s a good idea to get checked. Always check often and early, before a problem gets out of hand. It’s a good medical philosophy to have.