My boyfriend seems so distant Can someone help me?

My boyfriend of 2 months has seemed so distant with me lately. We always said we loved each other and talked about everything. And the other afternoon everything was fine. We talked on the phone and texted and he said he loved me. But that night, when we were texting, he said that had been talking to his ex but there wasn't anything going on between them. And I said "I love you" and all he said is "u2" now. And that's all he says now when I tell him i love him. I don't know what this means. Can anyone help me?