Why can I no longer keep large-ish meals down?

Ok, so, up until two months ago, I ate whatever I wanted, whenever I wanted. I’ve always been a small girl (5’3’’, 105 pounds), but I could (and would) eat entire pizzas and gigantic buckets of chicken wings without issue. I ate so much, it was ridiculous.

Two months ago, I decided I wanted to stop being so unhealthy, and I made a drastic change in my eating habits. I did not starve myself at all; I still ate plenty of food, but instead of grease and sugar and junk, I started eating fruits and balanced, healthy meals.

So, I did that consistently for all of December and was very pleased with the results. I felt much healthier, my body felt better, and I even looked more fit. I decided I’d like to keep eating healthy in general, but that I would allow myself to indulge whenever I went out to eat.

Well, every time that I’ve gone out to eat this past month, I haven’t been able to keep the meal down! This was never an issue I had before. I feel like my stomach must have shrunk because it went from digesting 4500-calorie dinners on a daily basis to digesting 600-calorie dinners. So now, whenever I eat bigger dinners at restaurants, I feel so insanely full, and I end up throwing up on the way home.

How can I fix this problem? I want to keep eating healthy in general, but I also want to be able to indulge in larger meals at restaurants without feeling horribly full and vomiting on the way home…