Have you talked to the GI yet? If not, I would suggest to call and let him/her know.
I had nausea and horrible diarrhea only after taking 2 days of 6MP, and I was hospitalized for fluids a few days later and told to stop 6MP immediately even though all my labs came back okay.
The dose and/or the new med could be the problem, but I definitely talk to the GI.
Female, Age 19, Dx w/ UC August 2007
9 Asacol, Rowasa, 1000 mg Canasa, Proctofoam, Rifaximin 2/day
Digestive Advantage (Crohn's & Colitis), 1 Florastor, 50 mg 6MP,1 Primadophilus reuteri, Remicade (3rd infusion 07/08), 2.4 g Lialda, 1 Forvia, 6 Colazal/day
*surgery tentatively scheduled for September