Oh wow, a massive initial post and 3 pages of answers already. Still, nicely paragraphed :-) I'll read the initial post and hopefully reply with something useful.
Starting arguments is not wise, regardless. Trying to discuss problems is a better option.
I'm assuming the "partner" and the "ex" is the same person, because my first thought was that one was past and the other present, but that doesn't seem to fit.
So before he was an ex he was being secretive about where he was. Ok that is hardly ideal, but it is reasonable to be suspicious when something as simple as where his friends are is deemed top secret. That wasn't wise on his part, maybe he isn't into the ideal that a couple is that close.
It is a fair comment that secret phone calls (which I assume you have proof of) is not good behaviour. From what you say it seems to me that he was not taking your relationship as seriously as he might. But I am aware we have one side of the story here.
Let's you down, fobs you off. Goes off with his mates (I assume more than one could reasonably agree to).
I'm unsure I need to read further. Stressing again we have but one side of the story it seems to me you are describing a relationship of convenience rather than a true partnership. you are there when he wants you, but at other times you can go hang as he wants to live his life doing just what he wants to do. I see little compromise.
I know I ought to read the whole of this thread but it seems to me you didn't really have a relationship worth the title to screw up. Are you not better off out of it, free to find someone who actually respects you (should you still want to share your life being with someone, that is) ?