I think I have ADHD but I'm just not completely sure if the signs I'm seeing are in line with the disorder...
Sometimes I think everyone has it.
Try here for basic info. https://www.nhs.uk/conditions/attention-deficit-hyperactivity-disorder-adhd/symptoms/
Like @dan1950 said it can be pretty difficult to know for sure. A lot of the symptoms are in line with other disorders. You kind of need to do a sort of symptom checklist to compare to ADHD and other disorders and see what makes sense. Along with talking to a doctor or professional of some sort.