the starting dose of Pristiq (50 mg) is FAR higher than the starting dose of Venlafaxine that we recommend (12.5).
https://www.dizziness-and-balance.com/disorders/central/migraine/treatments/venlafaxine.html
You can ask your doc for just venlaflaxine ER and start at 1/3 of the capsule. Which is what i did for VM. MDDS is a migraine variant too. I have same sensation as you lying down as everyone who has VM. My initial episode was set off by prolonged stress as well.