Please help me, he stopped talking?

I've known this guy since November, we me on a messenger app on my phone. He's in the same school but a year older. We talked constantly, day and night, hardly ever said good night because we fell asleep texting each other. I met up with him a few times and he tole my friend in January that he really liked me but at the time he had a girlfriend, the broke up about two months ago. I haven't talked to him in about a week, he stopped replying to me last Sunday but I thought it was okay as there wasn't much of a conversation going. Monday I messaged him and we talked for a bit, he said night and I thought he would message me but I haven't heard from him since. This happened twice before but now that we got closer and we're not talking makes me feel like he has another girl. I don't really want to message him first because my friend was asking him what happened and he said nothing and said he will talk to me. That was a few days ago and no text off him. What should I do? How can we talk for so long and suddenly stop talking ?