Why Do i Keep Making Decisions Without Thinking about Consequences?

I'm new to the community, but my marriage is in a really bad space because of a recurring pattern of making decisions and keeping them from my wife.  Two weeks ago, I started a new job and there was so much information coming at me, and I was excited to learn as much as I could so I quickly signed up for a $300 class without telling my wife.  She asked about it a few days later and I was defensive and shut down and turned away.  About a week ago, my Psychiatrist, NP agreed that I might need a small afternoon dose to get me through the afternoons because I was not having much success focusing.  I didn't tell my wife because I knew it would make her nervous and she would disagree with the decision.  This has been a pattern that's gone on for most of our 16-year marriage.  I get afraid to talk with her about things she will disagree with and so I decide it's worth the risk of not telling her.  Never works, I always regret it.  My question to anyone who is willing to respond,  is this pattern connected to my ADHD diagnosis and if so, what are some things I can do to start to prevent this from happening?  

I look forward to any encouragement and advice,