What makes you identify the problems as stemming from his being adopted? What kind of problems are they?
The best way to be a good girlfriend is to be wholehearted and as unconditional as possible, no matter if your boyfriend is adopted or not. But why do you think these are special adoption-related issues?
Well thats for example when he asks me questions about his identity; or when he goes thru an online search of a name for hours and gets irritated or easily angry aftewards... Or the way he behaves in families events (birthdayd, dinners etc), sometimes he'd start crying for no reason then get really mad at me for not understanding what he feels..
He needs to see to go to therapy.