Hi Hollie and welcome to the forum.
Everyone loses differently, depends on how much you have to lose, your diet, exercise, lots of factors.
So I don't think there is a normal, if you know what I mean.
17.5 kgs is fantastic, great work!
I never had any nausea or vomiting, so not much help there.
But if it continues I would be seeing your surgeon.
Good luck with your recovery and journey.