Unfortunately, people don’t change unless THEY want to. You can try to help, and talk until you’re blue in the face, but if he doesn’t see a problem and make an effort to address it, nothing will change.
Is he getting treatment for his ADHD? That could help both of you individually and as a couple.
The book The ADHD Effect on Marriage could help:
If you’re having these thoughts now, I’d strongly think about you’re upcoming wedding plans. It’s better to be alone than with someone who makes you feel bad about yourself and miserable.
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism