What he did to you in the past was really insensitive and had I been the one dating him,  I would have broken up with him after the first vacation...Luckily he found someone who was willing to get past that and give your relationship time to grow into a comitted two year relationship. Sometimes it takes time for men to put away their 'little black book' and fantasy relationships and accept the fact that they are in a comitted relationship. Now that you have had a chance to voice your opinion and he knows that his relationship with her both bothers and hurts you he knows his boundaries and what you are and are not comfortable with. Keep in mind however, You chose to move past everything that happened in the begining... so you can't continue to punish him for it. You need to accept the fact that he knows what he did was wrong and by telling him he can't speak to someone you are also damaging the trust in your relationship and adding alot of unneeded stress to your self. If you get upset every time he speaks to her,  he won't tell you he has spoken to her and it will all become a secret once again. Texting constantly and hanging out are not acceptable, but if he runs into her and speaks to her... don't crucify him for it. Set boundaries that both of you can live by (that go bothways) and keep the lines of communication open.
If it really bothers you and you can't get past it then i suggest, for your own sanity, you break up and start fresh with someone who hasn't hurt you before you even get started.