Too many vitamin supplements causing stomach ache?

i always have a sensitive stomach and i have celiacs disease (gluten intolerance) i have no eaten foods with wheat in years and none of my vitamin supplements have wheat they all say gluten free. i started taking biotin with B-complex (to grow out my hair longer) and i take them each once a day and then i also take Lysine (because i have herpes) and a zinc supplement too. the B-complex does not contain iron... why am i getting sick does this have anything to do with the vitamins is it too many? i do spread them out throughout the day