For similar reasons, I was not diagnosed until J was 32.
It may take persistence to get the correct diagnosis.
Why do you think you have it? You might want to list the criteria in DSM-V and write notes under each one, including doing some free-writing on ancillary issues that come to mind for each one.
Read about how ADHD manifests in adults and women, and document how what you read relates for you. Present the related info during an assessment. Also look at frequent co-occurring disorders and those that share some symptoms with ADHD (eg bipolar II). You might have more than just ADHD or you may gain insight into why one better explains your experiences rather than another. Don’t give up. It’s too important.