Its called being a mum..to a teenager!!!!
I really don't think there is much we can do, just have to hope what we already did was good enough.. my parents did a reasonable job with me, but I still did a lot of things without their knowledge, you do think you are invinciable and it will be someone else..
I guess if you try to keep him home more or start to check up on him, it will cause resentment and he will defy you.
Maybe ???just sit and have the casual talk about the things that have been happening lately.