Is my vitamin medicine causing me to feel weird in the stomach

I am on vitamin prescribed medication. I usually have to take it with food. Two days ago, I had lunch, like some tomatoes, and two pieces of quiche. I took the pill while eating at the same time. After one or two hours, my stomach felt a bit empty or weird. Its this funny feeling is if I am gonna throw up, but I won't. Its not really painful, just a bit like a mild upset stomach. Is it the medicine ?..

Firstly what vitamins are in the supplement? iron? vit c?

Secondly...are you on any other medication or herbal remedies? Because these could interact with it and cause negative side effects.