Last month I went to HK for business trip and the clients treat us big meals for few times. I experience overeating in one of the days where I'm feeling super stuff from breakfast, lunch and dinner. And then the next day I'm totally lack of appetite. From there I tried eating very small meals whenever I could. Then few days later only feeling better. But I'm started to feel nauseous when I eat a bit more.

Right now about 2 weeks have past, it seems that my appetite has shrink as I used to be a big eater. Last time I need finish two packs of rice box to feel full at lunch, now I can only manage 1 rice box. If I eat a bit more then I feel nauseous again.

What type of condition is this? I search online but all I could find is nauseous due to pregnancy (obviously not), migraine, food or lactose intolerance (unlikely), food poisoning or, warning sign of serious condition. Or I should visit doc on this?