My mom and I both occasionally have vertigo attacks for a few days in a row. I have so much empathy for you. I know exactly what it feels like to lie in bed and grab the sides because you feel like you're going to fall off it because the room is tipping. Or to feel like you're about to fall off a chair even though nothing is moving. I understand how you feel.
I am not sure I understand how often this happens to you. Do you have vertigo all the time? Or does it come and go? How often are you affected by it, and for about how many days at a time?
I have a question for you about the migraine issue. Have you had migraine headaches? Those horribly painful headaches where even light and sound make your head hurt worse? Or did the doctor just think the depression meds would help with the vertigo?
One fairly odd thing that one of my mom's doctors told her that actually seems to work is this. You do it in a sitting position. Straighten a hand out flat. Then, with the side of the hand where your pinky finger is, tap hard on the back of your head. You want to tap about halfway down your head -- about equal to where your ears are. And you can do it pretty hard (but don't hurt yourself!) Since vertigo is about the balance mechanism in the ear not working right, this action can sort of register with the ears and in essence tell them which way is up. It works for my mom, and she's had pretty bad episodes of vertigo, with all the same testing you have had. Maybe it will give you some relief as well.
What medicine did the last end prescribe for you?