"Why is it ok for him to be in a bad mood and be mean and talk rude to me..?"
"I suspect he is using again and I'm not ok with it but I can't get the truth, what should I do?" (You're asking the wrong questions!!!)
The question you need to ask (yourself) is; "Why am I staying with a man who treats me like crap?"
Since we have no control over what another person says or does it's important to focus on what we do have control over which is ourselves. No one is "stuck" with anyone. Sometimes we get so caught up in (our problems) that we lose proper perspective. If you had a daughter in the same position and she asked you for advice....What would you tell her? You have to be your own best friend!
The behavior and the drug issue you described would be "deal breakers" for most people. Being in a committed relationship does not mean you're not entitled to have "deal breakers". Anyone who loves themself sets boundaries! "If you want something different then YOU have to do something different". "When we change our circumstances change." Time to move on! Best of luck!