Ok I'm 14 and ADHD diagnosed friend has told me on multiple occasions that display symptoms of ADHD so I checked online (ik that's not exactly reliable source but it's the only 1 I have) and I related to quite a few of the feelings described. I tried to tell my mum and ask if I could check it out with someone professional and she said I was just making it up in my mind so now idk what to do and idk if I even have it or not.
Have a look at this post for more information about ADHD and how to know if you have it. If you go through the process indicated there and you still think ADHD is a possibility, talk to your mom about your symptoms and how they impact your life, without mentioning ADHD. Tell her that you would like to find out why you have these problems so that you can get appropriate help.