Frustrated baby whilst nursing

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The last couple of days my now 6 weeks old gets very frustrated while nursing half of the time. He lets go of my boob and wants back on immediately constantly and groans and screams and violently waves his arms around. I think it’s caused by him having cramps. When he lets go I try to burp him, but when moving him away from the boob even a tiny bit he starts screaming.

Anyone any idea what could be the cause and what I can try to help him?