Well speaking as an Alpha male personality.
I am in your shoes also. So your personality has nothing to do with it.(my view)
My wife and I just started in to poly and it been a F***ing emotional roller coaster for me. Trust me its been REALLY tough at time and draining beyond all I had to muster. So your not alone.
Do not FORCE your self in to changing your personality to fit the poly life. I did and it was really emotionally draining and painful to the body.
I was told my a guy friend that was mentoring me, as well as the girlfriend. To try to go with the flow.