The son has two lower teeth, he started to bite frequently during brea…

The son has two lower teeth, he started to bite frequently during breastfeeding, at night I can't explain that it hurts him, he doesn't even open his eyes, and in the daytime I also can't be emotional, I can't bear the pain until tears. I don't know what will happen when the upper teeth come out. What can I do? I'm afraid of breastfeeding already, I postpone this moment, the nipples are buzzing