Refusing to nurse?

Up until a few days ago, my baby would nurse when he was tired. He’s 3 months old. Suddenly he can’t be soothed when he’s tired. He cries and cries no matter what until he eventually falls asleep. I try to nurse him but he refuses and just gets upset. I’ve tried rocking him, putting him in his swing, carrying him around, putting him in his crib for a few minutes, nursing him. I’m at a loss. Has anyone experienced this or now why this might be happening? 😕