Is my boyfriend on drugs? How can I confront him?

I few months ago I jokingly asked to look through my boyfriend's phone's search history. He immediately got defensive and warned me he was looking up info about painkillers he found in a cabinet around his house. When I saw him searching different stuff that same day, the dangers of certain painkillers/dosages, he suddenly changed his story and said he was "looking up how dangerous the drug was for a coworker who has a problem." I know his life. He hardly talks to his co-worker.
Now, two months later, I was alone with his phone and checked his history to find him searching about a ABG 15 morphine pill and how to get high off of it, and what the high is like. He no longer works at the job with his coworker and they text rarely so I don't think thats it, but for some reason he has interest in opioid pills.

I KNOW it was wrong for me to look at his phone and I shouldn't have, but what is going on? I've known many addicts and his behavior seems normal - except that he is constantly exhausted at 28, pees every 20 minutes, and seems to lack emotional/physical intimacy, even a sex life. The longer we are together the longer I notice he's very reluctant to be truly intimate and even share his past with me. I heard lack of emotional closeness is a symptom. Could these be signs?

I don't know how to confront him but I want to very soon because I'm very against drug-addiction. How do I tell him I looked through his search history? I know he will get mad, but I need the truth. How can I get him to open up to me? Is something going on?
Is my boyfriend on drugs? How can I confront him?
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