I think I might be sick...?

So, these past mornings, I believe like a week or so, I've been having breakfast like usual before I go. But every time I've eaten breakfast, I've been getting nauseated in the stomach and feel like I'm going to puke. I ran to the bathroom, but I didn't. Then this morning, I ate my breakfast and my stomach got really upset. I ran in the bathroom and ended up throwing up. It wasn't a lot, but it wasn't just that little bit you get in your mouth, either.

I've been trying to think of anything it could have been that I've eaten. I haven't really had any healthy breakfasts lately, either, so maybe that's the case. I've had poptarts and milk for breakfast, except for yesterday I had a bagel. And I know it wasn't the bagel because I had one later in the day and I didn't get sick. I also had some chicken yesterday that I didn't eat much of because it tasted kind of off. So maybe just some bad chicken?

It usually only happens in the morning, though, the rest of the day I feel fine.

What do you think it could be? Help please?