I'm surprised they didn't warn you... I'd say its completely normal but I suppose you should take the advice of someone that's actually had vision therapy over mine! The reason I understand what you are going through is because I've had vestibular therapy and the exercises start out all eye movements. I have eye issues also.

The day of my first session was the worst, the next day wasn't great and then I was back to the usual. I don't know how long it will last for you but today will probably be the worst.

Hopefully someone that's actually had vision therapy will answer you with more helpful advice

Just wanted to say I know what you're going through and its most likely perfectly normal! No pain, no gain. Good luck with your treatment and I hope you are feeling better soon! On days I have therapy I schedule nothing the rest of the day and make sure there's leftovers in the house!

Take care
CC