Forget him. Try to find someone else in the group who can keep you posted on upcoming trips and make sure there is room for you to go if you choose to. Who knows his motivation? Only he can. But trying to figure it out will only make you feel bad. Let him go and if he decides to discuss what's going on with you fine. If not, fine. It's just not worth trying to read his mind over this. It won't help you at all. Don't take it personally. He's got something going on in his head that probably has nothing to do with you anyway.