I have reflux for a week. it started when i drunk sth very cold. what could it be? my stress about it makes it worse? also, i don't eat very well...

Hard to say: The most common contributing conditions to reflux are being overweight and smoking tobacco. If you have either, weight reduction and smoking cessation will help. At your age, i don't worry too much about needing a GI work-up, and would recommend using available over-the-counter medications, particularly Omeprazole 20 mg, once a day for about 2 weeks. If the reflux returns afterwards, see md.