Does falling asleep constantly during the day and feeling tired mean that i have narcolepsy?

Not really: Typically, it means you are not having restorative sleep at night.

Maybe: The most common cause for sleepiness duringthe day is poor night sleep and, too little sleep. Sleep apnea, a breathing problem at night can cause severe sleepiness. And, yes narcolepsy. You need an overnight sleep study to test for sleep fragmentation. You need a daytime napping test (mslt), if the overnight sleep study is normal. A sleep neurologist can sort this out.