PerSe…...in response to your question---"Why did I play second fiddle for 20 years?".....
I would propose that the seeds for your personal dynamic were planted in your early developmental years....and, that you brought this (these) dynamics as your own baggage, into the marriage....though you may not have been very consciously aware of them....
I think that uncovering how this happened is the kind of work that that a therapist can be helpful with (in addition to alanon)….
I do think that it is important to get this kind of insight, because we humans seem destined to repeat our patterns, if we don't become aware of what makes us tick and what our needs are....