G.♣.
It's rough, but you just have to hang in there. This is not that unusual for a 3 week old. It might take another week or two for him, but soon he will be eating more at each feeding and eating a little bit less often.
Please do not worry about not producing enough milk. As long as he has enough wet diapers, he's doing just fine.
Talking to a lactation consultant is a great idea. This will give you a much better idea of what is normal and ok and will give you a chance to ask specific questions.