There are some screening assessments for ADHD including the Adult Self-Report Symptom Questionnaire (ASRS) that you can find online. Not all providers will use that, though. Sometimes they will refer you to neuropsychological testing which is unfortunately not very helpful as it doesn't accurately diagnose ADHD. Usually as adults the best way to diagnose is through a good history and a good relationship with your provider. If your provider trusts you and can let you explain your challenges then it's likely that they will be able to help make a diagnosis if one is accurate or not.

That being said, it's also easy for providers to want to defer ADHD and focus on other issues as they feel more familiar with things like Bipolar Disorder and have a lot of stigma and bias around ADHD.

Personally I had a diagnosis of Bipolar Disorder long before I was diagnosed with ADHD. I was able to get the ADHD diagnosis after working with a good provider who spent a year and a half getting to know me and trying things like non-stimulants to help with my challenges. Ultimately I got the diagnosis and medication and it's been life changing. I hope you can have a good experience as well. Good luck!