Constantly annoyed son

Hi ladies, my son is 4.5 months old, and he sleeps well through the night. Since 3-4 days he has been extremely cranky during the day, constantly needs to be carried to calm down. He is happy if I'm carrying him or playing with him. The moment I leave him, he's crying again. Last two nights he's been waking up several times a night crying. He refuses my breast, and becomes quite only if I carry him n rock him. He used to sleep so well through the night, Nd now he's not. Has this happened to anybody? Any advice. I'm waiting to call his doctor, but I thought I would post here first.