Reaction to ivf drugs and trigger shot

I am starting ivf cycle this month. Had three failed iui before and we have decided to proceed with ivf now. During my iui cycles everytime after trigger shot (ovidrel) i got severe stomach pain. At one cycle it was like labour pain. The doctor said it has nothing to do with ohss since i always had one follicle only. I am now scared about the ivf drugs since its more powerful than the iui drugs. Has anyone had any adverse reaction to ivf drugs. Pls send some encouragement and tips or things to discuss with the doctor my way.