Should I be worried?

What does he talk about with your friends? It could be he is insecure about something, or something has happened that he wants to tell you in person, and he's afraid he'll slip up when talking to you. Think about it. Most of the time, we invest our time considering all the possible negative options, to no avail. Even if the negative happens, it is not worthy of the time invested in it. Most likely, there is a good reason. If not, don't worry about it. Invest your time in things that are fulfilling and encouraging. When he gets back, it will be time to discuss what he has done, or not done.
Worry empties your emotional account with no promise of a return. Invest in things that give you a positive return, so when something happens that you would have worried about, you have enough of an emotional balance to stay in the positive.

Well you need to ask him what's up. You need to ask him why he is being so rude and why he does not put your feelings in consideration. It sounds like you deserve better treatment and faithfulness than that

thats pretty messed up. why would he be calling your friends and not you if you guys are together? something is wrong. confront him.