My boy is almost three weeks old and hes eating...

My boy is almost three weeks old and hes eating expressed breast milk in bottles, no formula at all. He groans and kinda whinges like mad allll the time!!! I burp the crap outta him he does like three big belches with every bottle but still this horrible groaning noise. I think it might be wind but i can wind him for the entire time between feeds and hell just fall asleep groaning and when he wakes up keep going! Does any one know what this is?