19 year old son cannabis addiction

Hi I feel so alone, this is the first time I’ve written about this, my son at 16 started college and also started cannabis, he’s 19 now and I am at a loss, his room is dirty and messy, I have refused to clean it anymore, he knows not to keep or smoke in the house, he then gets a car and now uses it to smoke in or stash stuff. He doesn’t drive by the way he was learning but failed thank goodness because I don’t want him driving while using. He showers every day and has a part time job but no interest in working for a career or anything that would take effort, he does a trading app and thinks this will make him rich! I do a bit of washing for him but he wears dirty clothes and his hair looks scruffy basically doesn’t care about himself or what people think but he does go to the gym 🤷‍♀️ I don’t know what to do his dad doesn’t live with us anymore left when he was 11, only my 16 year old daughter and my partner who doesn’t want to step on any toes, his dad said kick him out if he’s not following my rules but that isn’t the answer so basically I feel alone and don’t know how to help my son especially if he’s not seeing anything wrong.