My Brother Stopped Using, but He's Still A Jerk! What Do I Do Now?

It sounds like you're grieving for the kid your brother used to be and wondering (and hoping!) that the sweet kid comes back – and that is your real question. Is it possible that he has an undiagnosed mental health condition? Absolutely, yes. 

It's also possible that there is something that happened to him (that you may or may not be aware of him) that fundamentally changed him.  It's possible he's still (secretly) using drugs or drinking, or has switched to a non-chemical addiction (such as gambling, or sex) and is still displaying addictive behavior.  

None of that is really the point though. The point is that the person he is now is not the person he was then, and you want to know whether the sweet kid is still in there. 

I honestly don't know, without knowing more about you, and him, and the situation, whether that sweet kid is still there. Is it possible to talk to him about this? Perhaps just honestly saying “I remember when we were kids, (this thing) happened, but now things are like (this). Why is that?”

Do you or any other friend or family member have some sort of influence over him to convince him to get an assessment? Have you ever noticed symptoms above and beyond 'being a jerk' that might be depression or anxiety or trauma? 

Some other questions for you: Can you avoid him when he's 'being a jerk' or are you stuck with him? Are you ever afraid of him? Can he sometimes be talked into mellowing out and being 'halfway decent'? 

I might start by picking a time when he appears to be in a pretty good mood, and let him (gently) know how you feel, including your worry that maybe he's depressed or has something else going on. If he's receptive, offer to go with him to get assessed, or to help him in some other way he might tell you he need. If he gets rude or acts like 'a jerk', it might be time to assess how much you want him in your life, and distance yourself.

The first couple of years of recovery from an addiction can be very stressful times. It's possible he's still experiencing significant cravings, has guilt and shame from his addiction and/or things he did while actively using, or still has some brain chemistry issues going on.

It sounds like you're coming from a place of love and concern, even though you also sound frustrated and annoyed. I don't know if you have the power to change the road he's on, but I think that if you speak to him from that place of love and concern, you'll feel better about yourself, and possibly be able to find a new path that accepts your brother (oddly, sometimes when people feel accepted, the 'jerk' stuff starts to go away). 

I can't promise he will change or seek help. But you're asking good questions, from a good place. He's lucky to have you in his life regardless of how he's acting.