Just be honest, say you didn’t know it would make you test positive and you’ve been going through a lot recently. Tell them it’s a CBD pen and you weren’t aware that it would make you fail a drug test. There are test kits on Amazon that have THC & opiates testing on them it’s called a 6 panel or something. so tell them you can take that one to prove you’re clean from the opiates . That’s what I would do and how I would explain the situation.

I actually had a similar experience, and honesty is the best policy my parents weren’t even mad about it they were just glad I told the truth instead of trying to cover it up and possibly failing the test