You should take his cue and date other people. I know it’s not what you want to hear because you like this guy, but when a man tells you he’s not available to you, you should respect that — and yourself! When he says you’re free to date other men, he’s giving you the parameters of what he’s willing to contribute in the relationships, and in this case, it’s no commitment, and an unspoken gentleman’s agreement that he is free to date other people, too. That he told you he isn’t interested in dating other people is just his way of trying to hold on to you, but letting you know that both of you are free to do what you want with others. In fact, since you say he’s suddenly acting weird, and isn’t calling you as much, I suspect he’s got someone else he’s interested in that you don’t know about.
There’s really no reason to date someone who’s not available to you for what you want, which I assume is a long-term commitment or marriage. You have to keep your eye on the ball to avoid wasting your time, and your emotional energy. I can tell you’re committing to this guy, emotionally, and when you find out one day he’s involved with someone else, you’re going to feel betrayed, when the truth is, he’s being very upfront about not giving you any commitment or even dating interest.
So, move on, and find someone who is interested in you enough to make that commitment you’re looking for. 🙂