Did you have problems with pda in the mono relationships? Do you want to keep it a secret that you are in a poly relationship? If so, what are your reasons? You shouldn't be "required" to show pda, but if there are insecurity issues or some sort of shame involved, you really should take the time to analyze that. Maybe you're suited to poly, maybe not. Without knowing you, I have no way to say. But you should be comfortable and honest with yourself and likewise be honest in your interactions with your gf.
Me - Mostly mono female, 39 yrs old, married to Leo.
Leo - Poly bi-sexual male, 37 years old. Married to me and looking.