First thing to remember is that you are the parent - he is the child.
Second, stop allowing him to go hang out with older teens - nothing good is going to come of that.
Third, without more background info it is really hard to know what your past relationship with your son has been and what his past behavior has been.
But it does sound like something has gone drastically off track with him. If he where mine I would take away all privileges, stop allowing him to go out with older teens, never leave him alone, and do a drug test on him. Oh, and make him quite smoking! Really, where is he getting the ciggs from? Then I would run, not walk, to the nearest therapist and get us both into counseling pronto. If your health insurance doesn't cover it, or you don't have insurance, there are many sliding fee scale services available - check with your local health department and/or associated Catholic Charities.
My son is 15 - he is still not allowed to go out - especially not with older teens in cars when I don't know what he is doing or where he is going. He has friends over, he goes to friend's homes - but adults, that I know, are always present. I know what he is doing and when he is doing it.
13 is a tough age - but, if he has gone off track, you have a chance to get him back. It will not be easy - you have to fight for him.
God Bless - my prayers are with you both.