Marijuana's effects on sex drive

Does anyone here know to what extent marijuana can affect a man's sex drive? I've read that the THC affects testosterone levels and can eventually lead to impotence problems.
My boyfriend smokes it and has the lowest sex drive of any guy I've ever known. Of course this is a problem! I don't know if I can convince him to stop smoking, but I just want to know how much the actual pot smoking could be affecting him or if it could be something else. He also eats terrible, so that doesn't help.
I don't think occasional use affects sex drive that much, but he smokes it every day. Has anyone else had any experiences with smoking it and noticing a lower sex drive? Any suggestions on how to increase sex drive? Tweet