How long oxycontin stays in your system?

My husband has been snorting oxycontin for almost a year and I found out a month ago. The only way I will stay with him is if he is clean. I've been urine drug testing him at home. I bought oxy tests, not just for opiates. He says he has been done with oxy for 2 weeks, but I just tested him and it was negative. Does anyone know how long oxy can stay in your system if snorted?

: http://alcoholdrugstreatment.info/how-long-oxycontin-stays-in-your-system