Teething phase?

Hi. Doc said that my son is in teething phase, teeth number 7&8 are coming out. My son refused to drink plain water or milk. And he won’t open his mouth because he’s keeping his saliva in it. He won’t swallow it. Whenever it’s full enough, he’ll just open his mouth and let it drooled out 😅 is this really a teething phase? Byw, doc confirmed that there’s no ulser or tonsil in his mouth. Any suggestion that can help him taking fluids so that he’ll not dehydrated. Thanks in advance!