It it makes you sick, don’t eat. It may just be that certain foods don’t sit well with you for some reason or it could just be personal taste, most of us have some foods we just can’t stand.
As long as you are getting plenty of fiber and necessary nutrietns from other sources, there is no need to force yourself to eat things that make you sick. However before giving up completely on something, try different recipes of banana to see if that helps.