From my own personal point of view as someone who is still an addict and struggling like nothing on earth with it is…. I bet this guy loves you like you will never imagine, everything you have said reminds me of well ME…. its so hard too understand, when your on it there’s no point trying too talk, you need too just let him be… without being big-headed, I’m the most outgoing chatty people person ever, every1 is my best friend, when I’m on it all I want is too be on my own and no1 too talk too me, the flirting bit is probs self esteem, he wants someone too give him a tad of attention thou I do believe he wouldn’t cheat (even thou I don’t know him) i haven’t but get accused all the time, all I want personally is too stop it but I’ve not found a way yet, I really hope you stand by him and give him all the support he needs, he can’t do it alone, even if yous have no future… he is your best friend, struggling too talk about it and needs you more than you’ll ever ever ever know.