As @NK346f2849X127d8bca260 says you really do need see a dentist,
Nausea could be coming from an infection which is causing the pain or something else
Are you taking anything for nausea when its present? Has this toothache and the associated nausea affected your eating / appetite? have you lost weight as a result of this?
out of interest what painkillers are you taking on those weeks you need them? is it otc painkillers or stronger?
when did you last see a dentist? do you take care of your teeth, gums and mouth
i had a dental phobia for many years, it took time to recover and now im naturally relaxed there so getting to that stage from someone who couldnt pass the premises of nearest place was a personal journey
The extreme nausea could also be coming as a body response to pain from tooth. Do you have any sea bands to use for accupressure point on your wrists to help nausea.
Keep sitting water if you can and take it easy, I hope you will be able to find help and maybe support to see a dentist to stop the pain and nausea