If you are into your 4th day of nausea AND not eating, then it's time to see a doctor.
Just my thoughts... If nothing in your life has changed, no new drugs, whatever, it's a sign of something. And you are assuming that it's a part of your disease. That may not be the case at all. In any event, a multiple day fast with nausea isn't something to ignore. Your doc may want to up your meds, run tests, or tell you it IS part/parcel of your disease. at least this way he/she is in the loop, and able to do their job. OK?