You know when you're about to throw up, you feel nauseous and sick. lately i've been suddenly throwing up little amounts of food i've eaten, but with no signs of nausea. it just happens when i least expect it. why?

It is abnormal to vomit randomly without any trigger. You are not nauseous so pregnancy is unlikely but urine test should be done if you are sexual active and you've had unprotected sex. Other than that, you should make a diary about the food you ate when you vomit, and time, body position when vomit occurs and any associated symptoms such as headache, dizziness, etc. I assume you don't take meds.