Morning sickness or something else?

So I'll be 25 weeks on Thursday, and today I ate breakfast (a big bowl of cereal). And within like 2 hours I felt really sick. I got sick and felt just fine. Then about 20 minutes ago I was hungry again so I just had a salad. I'm wondering if it's cause I need to go from 3 large meals a day to 3 small meals and 2-3 snacks. Can anyone give me insight? Or is my morning sickness making a come back...