My 17 year old smokes marijuana

My 17 year old smokes marijuana frequently. I’m worried about his health (physical and mental). We’ve tried many different approaches to address this, but nothing works. He’s pretty much committed to using. My thoughts around this are I should’ve been stricter with him, and fears for him around addiction and his future. My feelings are worry and shame that this is somehow my fault. I respond to my feelings by trying to numb them (over drinking, shopping, eating) or obsessively researching how to reach him. Any ideas on how to change my model/s?