Please do NOT simply take medications if it is not prescribed to you. Metformin is an oral antidiabetic agent and amlo is a calcium channel blocker (BP lowering drug). They do come with certain side effects.. So please, have a proper appointment with a healthcare professional.
Maybe u are just getting hypoglycemic, hence the sleepiness.

Not sure TS will ever see these messages, but well, it can serve as a reminder to public..