Could unprotected sex with a Heavy meth user make me test positive?

I have been clean and sober for nearly 4 months now. I begged my dr to help me with a combination of medicine to help me get and STAY away from Meth. I can honestly say I haven’t touched it since the day she started me on this new regime, however I tested positive for meth in my last drug screen. I know I haven’t used and I would be honest with her and tell her if I did, but I didn’t. My off again/on again bf is still a very very heavy user and we do have unprotected sex. I’ve tried to think of any possible way I could have tested positive knowing I didn’t use. I’m so frustrated. We did have sex the night before I went in for my last appointment and it’s the only way I can explain being exposed to it. I have nothing in my house. He doesn’t smoke it around me. He does do booty bumps and unless it came through him into me, I have absolutely no idea of how I showed positive