There are a few options, and I honestly say go for all of them at once:

1. Take some (legit) self-assessments and see how they feel. E.g. https://embrace-autism.com/asrs-5/
2. Find some ADHD resources. See if the techniques and tools help, or at least feel sensible. E.g. the book How To ADHD or various Youtube channels.
3. Seek out a psychiatrist to assess you. It may or may not be ADHD, but something is bothering you that needs attention. They are usually good at figuring that out.