What a terrible feeling it can be to be the detective. The personality changes you explain are something I know well. The pupil checks were something I did on a nightly basis until he started catching on and getting defensive. The thing is, people who are not in his life in the way that you are (his friends, family, etc.) will not see the manifestation like you do. That was so frustrating to me until I realized his choices are not my responsibility and I have no control over them. The first time I could tell he had used I gave it a little time to collect my thoughts and be calm. When we were alone and he seemed calm as well I asked "Did you take something today?" He sat quiet a minute and responded "Yes, I got two pain killers from a guy at work" Instead of giving a lecture I asked him how he felt about it so I could get a feel of where he was at. Sometimes he would make it out to be not a be deal. This particular time he expressed shame (I believe it to be authentic) but the shame wasn't enough to stop him from spiraling. When I asked him about it this time (unlike times in the past) I was giving him all the room to talk and only gathering information for myself. Once I stopped obsessing over his using and taking care of myself while observing his actions I began to see things differently and the anxiety I had while being a 'detective' went away. I became stronger.