Hi, and thanks for your medical question on eHealth forum
Waking up in the middle of the night with headache, vomiting, loose motion can be due to food poisoning. It could also be intolerance to some food item. So look back and see if there was some common food item that could have caused this.
High blood pressure, migraine and benign intracranial hypertension (due to impaired CSF absorption) are the other possibilities.
It is difficult to comment beyond that on net. Please consult your PCP and try and get an appointment for a neurologist. Hope this helps. Take care!