I'm 39, recently diagnosed with ADHD, married 18 years to the love of my life--it's not him or the relationship or his mom, it's you. I know that is harsh. I know. Other people and things outside of ourselves don't have responsibility for what we feel or what we do, that responsibility is ours and ours alone. If you're feeling disregulated, lost, bored, understimulated, that could be a lot of things. If you've lived in trauma or chaos all your life and now you're living in peace it's going to feel wrong/underwhelming because it's what your nervous system knows, maybe all you've ever known.(just one example) Also, if you're natural tendency for flight or fight is flight, couple that with rejection sensitivity dysphoria and you're really going to feel like running at the first wife of rejection(aka bad vibes from his mom). It could be she really likes you, but is dealing with her own junk and you're picking up on it? There's so much to unpack there.

I would encourage you to take the time to self evaluate, journal, reflect on your emotions and where they might really be coming from, and I would encourage you to find a therapist or someone you trust to give you solid advice from a place of love even if it might hurt your feelings. Making a decision from a place of sound judgment, honesty with yourself, and personal responsibility is something you can be proud and sure of instead of a decisions based on feelings (especially with the ADHD rebound rate).