Getting ur partner to believe in your intentions

Non-ADHD spouses, how did or have ur partners gotten you to believe in their good intentions again? I struggle with extreme emotions and tend to avoid difficult conversations, but also can get overly fixated on a potential issue and "pick" at my wife until she loses her cool. So that even if it wasn't an issue before it is now. I can't seem to find a balance between these two extremes so now when I don't ask about something my wife assumes it's because I don't care and do not want to know. She doesn't believe me when I tell her I'm afraid to make her upset by picking at a problem and has just concluded I don't care enough about her to engage. How do I get her to believe I want that without engaging every little thought and "picking" at her? 

the short answer seems to be engage on the right things but honestly if I knew how to do that I wouldn't be in this mess. I feel like I need her input and participation to help guide me to the right issues to engage and the right ones to ignore but can't get her buy in because she believes I don't care and am just placating her.