Addiction. Please help!!

I made a post maybe about a week or so ago. It was about my 18 year old admitting being addicted to percocet for 2+ months, but refusing going for treatment and said he will try to stop on his own, I didn't believe he will but I can't force him to do anything he doesn't want, after that I caught him 2 times crushing percocet and sniffing it, both times he promises he will stop, but of course he hasn't and that's what I expected. Today it seems like he is out of it, and he's acting really weird, crying, then laughing uncontrollable, then starts slamming doors and is begging me to give him one of my husband's pain medication(my husband had surgery 3 weeks ago, and was prescribed to take as needed but he only used 4 pills of it, because he doesn't like the feeling it gives him and has been taking just tylenol instead) he's begging me and crying and saying he's in so much pain and really needs it. Of course I tell him no, and that he needs help but I am heartbroken and really lost on what to do. I can't believe this is my baby, I feel like I'm dreaming. Idk what I'm asking for, but I need support and more advice on what would you do, if in my position? Tia! Hope everyone is having a good day!

Edit: Thanks for all the advice you gave me. I truly want to help him, but he is refusing completely. It's very hard seeing him this way, I wish I can take his pain away and willing to do anything in the world to help him, but he is refusing and only thinking of how to get his next dose, crying, screaming and tbh it makes me scared. Also I have another 9 year old child in the house and seeing his brother act this way is truly affecting him too, he doesn't know what's going on and I'm trying to keep him busy while trying to deal with my 18 year old at the same time. It's truly the hardest thing I've ever dealt with in my life..