i know exactly how u feel now ... coz i've been having bad teeth since i was very little. i think u might need a root canal (度牙斤). if that's the case, usually the dentist will ask u to take the antibiotic medication first before having the dental work done.
the best dentist i ever had in macau was: 張明光 who's graduated from japan. i saw him when i was very little, so i don't know if he's still around (maybe in his 50s now). he used to be in 新馬路大豐银行大厦, but now maybe u should check the yellow page phone book. he used to take insurance. i think it's quite expensive if u don't have insurance.
another dentist whom i saw when i was older: 鄺少華 who's less "pro" than 張明光 though. 鄺少華 who's mentioned by another BK friend earlier, is ok and he charged not much. i went to 鄺 for root canal, but i don't like that he suggested to take out another tooth which might be unnecessary.