Side effects of gem/doce treatment

I had 6 weekly treatments of gem/doce following turbit for nmibc with little side effects. I started monthly maintenance treatment of gem/doce and developed severe migraines lasting 36 hours before starting to abate. Also have severe dry heaves lasting several minutes each time and occur about once an hour for about 6 hours. I have experienced this for each of my first two maintenance treatments. My third is coming up soon and I am discussing with my doctor about discontinuing treatments. Has anyone had any similar experiences, especially the migraines. They are very severe and debilitating. Any advice or insight would be appreciated.