I have major depression and i am on sertraline and mirtazapine. lately, all i do is sleep sometimes for 2 days straight. i don't understand why?

Recent addition?: Zoloft (sertraline) is an ssri; Remeron is a tetricyclic. Both are antidepressants. If you have recently started, increased, or made a change with one or your meds; that could be the reason for your sleepiness. Hopefully, with time, this will pass. If you are established on these meds, then it sounds like something is off; and should be re-evaluated by your fp. You may actually need a higher dose of remeron!

Sleepiness: Remeron (mirtazapine) can cause sleepiness. Decrease meds which are sedating after discussing it with your doctor. There are other options.