What Causes Dizziness In My Sleep?

Hi, my name is Lela. i've a question about dizziness. As i was sleeping one night i was experiencing dizziness in my sleep, i woke up i was very dizzy, went to the bathroom my heart was beating fast. I drank a little water and tried to puke. I couldn't at the moment. I waited for a while getting very dizzy and i tried to puke again till this green watery "gall" came out. After half an hour i was ok, not dizzy but just a little headache. This has happened to me before, happen's to me every 4-5 months. What should i do?