Why do i sleep 12+ hours everyday?

If i'm allowed to sleep in, like I am now because of summertime, i'll always sleep about 12 or more hours and its eating away at my time. During the school year, i thought my body just did that so i can get back some of the sleep i miss during weekdays ( i slept like 5-6 hours or less) but now its summer and i can't even get up before noon. Like even if i set an alarm and put it across the room, i'll somehow convince myself to get up and walk all the way across the room turn it off and go back to sleep, and i'd be okay with, then when i'd wake up later i'd be pissed that i didn't wake up. Why is this happenening and how can i fix it? its really starting to bug me smh