My husband is using drugs but wont admit it. How do I confront him?

I have been with my husband for 17yrs. We have officially been married for 2 yrs. In the past I have found evidence that proved my thoughts correct , but they were settled so I thought. Now, recently I have been finding drug paraphanalia in his clothes and in the laundry. When I confronted him about them, he said that they were old and that he is not still using. I know that he is lying. I dont know where to go from here.