Someone asked what is meth.. It's meth amphetamine, a very concentrated form of speed, with an incredible rush. This stuff is absolutely destroying SE Asia. Truck, taxi, bus drivers are on it to keep awake. It's huge in the party/dance scene. It's extremely cheap to make and readily accessible all over the planet.
I used meth(we call it ice around here) for a couple of years. Loved the stuff. Thought it was the one drug I could handle,
until I started to have paranoid delusions, ground down teeth, insane outbursts of anger and the loss of a very sweet girlfriend. The final realisation was waking up one day in a panic attack. I cut back on my usage, but they didn't stop. Stopped using and the attacks continued for at least another year.
Advice? Leave him right now. He's bullshitting you about being clean. You stay and you will find his gear eventually, hidden somewhere or your friends will tell you they saw him scoring.
When he proves to you he's back on track, take it slow. How do you know when he's clean? Look in his eyes.
I now am a counsellor for teenagers and can honestly answer when they ask me "You know so much, do you use?" No