Is this an eating disorder?

I was wondering if this could possibly be an eating disorder or a physical problem or what?:

Technically, according to my bmi, I am underweight but it's just because I'm tall with a high metabolism. When I eat, I don't eat a big amount because I eat slowly and get full fairly quickly. It seems like I just have a small stomach. Then, i guess b/c of my metabolism, I get hungry again fairly quickly (I've always done the previously mentioned stuff my whole life, so I'm not worried about it, it was just background info), but then recently, after every time I eat, I feel nauseous. I'm pretty phobic of vomit and I know the damages, so I'd never make myself puke but I definitely have the urge. I don't feel self-consious about my weight. I'm content with my body. And I don't actually skip meals or purge, so I can't tell if it is maybe an eating disorder, a physical problem, or nothing?

Thank you so much :)