Minny, it is possibly frustration - boys can be a little impatient! But I wouldn't worry too much about the sleep after goats milk hun. It doesn't mean he's not getting enough from you. Goats milk has a totally different mix of proteins than human or dairy and he was probably sleepy because it was harder to digest. OT, but is there a reason you are using goats milk? If you are worried about your supply, the best thing to do is to offer more feeds for a few days.

The other common reason for biting at around that age is that the attachment isn't good. It is so easy to just let them attach in any position at that age but sometimes this can lead to pain. Perhaps for a few feeds you could try paying careful attention to his position and make sure he is in nice and close with his head tilted like he's drinking a half empty glass of water.