Speaking as a doctor who treats ADHD, it is diagnosed based on symptom observation.
Try this complete list of ADHD symptoms to see if it applies to you:
List Of ADHD Symptoms:
Also, take the free ADHD Test:
My boyfriend has ADHD and only sleeps for 5 hours a night tops. He constantly makes odd noises and doesn't stop moving. He also has a foul temper and has tantrums anywhere, even in public. He even had one in Starbucks the other day and threw money on the floor. It's very hard for him and everyone else as he is nearly 21.
It sounds to me like you have it.
I would suggest you keep onto your Mother about it. Not getting help could seriously effect your relationships and your professional life.
I would suggest following a diet free of sweets and additives instead of taking pills. I took Ritalin as a child because they thought I had ADHD and so did my boyfriend. We now both have unexplained health problems and so do all the other people I know who took it as children.
Ask the school (the nurse for example), I'm sure they'll help you. Tell your mum how worried you are about this then she'd have to take you to see an expert. Don't worry, I hope that helped a bit.
Drugs given for ADHD are on the controlled substances list and have shown to stunt growth and in longer term studies show damage to brain cells. Nutritional studies shown 80% reversal of ADHD symptoms within 2 weeks of a processed free and chemical food additive free diet. L-Theanine is a natural substance from green tea which is used in Japan for attention problems.
It sounds like you do have ADHD show her that you have all the same symptoms people with ADHD have, and ask her to take you do the health clinic just to make sure :)