kidney stone questions

I am 3 weeks post op RNY. Just finding out that the incidence of kidneystones rises dramatically with RNY patients.  I have already had 9, and am borderline hyperparathoidism.  I have not had a stone for 21 years, due to tx with Hydrochlorothiazide, by an endocrinologist.  I am VERYnervous about this, please tell me ways to decrease my chance to have reoccurance of kidney stones!
I already drink nearly 2 liters per day as well as take the Hydrochlorothiazide as ordered daily.
Thanks in advance for your help--I sure hope there is a way to keep me from having stone reoccurance-my previous ones were calcium based.