BD and nausea

I have been on azathiroprine for about 1 1/2 mo. at first no problems side effects etc. now I find that if I take the meds in the morning if I have had anything like a salad the night before for dinner I throw up with in 10 min. or less of taking my meds. has this happened to anyone else? My doc just prescribed phenergan for nausea I hope it works. I just want to know why eating healthy makes me sick. Any advice would be great, thanks, Denise