I can eat cheesecake but I can't eat cooked vegetables...

I don't understand what's happening. In the past few days, many guests came to visit me and brought cakes and pastries. I ate some of them and nothing happened except for a little bloating. I had severe constipation before and after the surgery, so now that a week has passed, I decided to eat fiber to help. I started with cooked vegetables with white rice, and when I ate them, I started to feel nauseous and felt like I wanted to vomit. Is this normal??