Can you use drugs while on suboxone?

[Meggy13465]

My husband has battled with addiction since having chest surgery. We went through some really rough times of him hiding and lying about his addiction. Since November 2016 he has been on suboxone and all seems ok. He checks in with his doctor once in a while and gets drug tested, etc
However,  recently he has been kind of acting funny, reminiscent of how he was when he was using. His eyes had this glazed over look a few days ago which got under my skin as I remembered that look and he got real defensive saying he was just really tired. The next day we had sex and he took forever to orgasm which used to be the case when he was using, and is not usually a problem at all. Lastly, last night (albeit he worked hard cleaning and mowed the lawn during the day, then smoked pot at night), we were watching TV and within minutes he started nodding out. I suppose he could have been just tired but who falls asleep that way? His head staying upright and all. All of these "signs" have got me on edge but he has this "how dare you question me" attitude that makes me feel bad. I know he has said hes proud of himself for being clean for so long but I also know some people claim to be clean but aren't.  Anyway,  my question is - can he take this med and mix it with something to act this way? Or take more than he should to display these signs? Or is it possible he stopped and switched to an opiate? I know they drug test him but he seems to have it down as to when so he can get away with stuff.. I.e he knows when to smoke pot and when not to. Or , am I just being paranoid??
Help please! Thanks