I've fasted 4 days in under 2 weeks (no water of food from sunrise to sunset). 3/4 of those days i've vomited after just breaking my fast. never happened before even when i've fasted a whole month straight (ramadan). is this normal?

This is NOT normal. I suspect you ate hard to digest foods and/or a large quantity, stretching the stomach and yielding this reaction. After fasting try a dairy meal and easily digested foods. Write back if this continues. Good luck

Fasting is from food. Do not fast from water as this is dangerous. To break a fast, it is vital to start slow. For the first thing, drink a little juice or sweetened tea. If you can keep that down, follow with a small piece of fruit (apple or banana). Introduce small portions over the next hour or two as your stomach tell you it is OK. Since you have fasted from water you are probably dehydrated.