i think what she was prob trying to say is that bub might be getting too much foremilk and not enough hindmilk.
Ie feeds and stopps after let down or you swap too early on sides and they get the sugary thirst milk at the beginning of a feed and not enough of the fatty milk at the end.

Try after bub seems to have finished putting him back on the same breast before swapping sides and see if it makes a difference,

And no you cant overfeed a BF bub!