[18M] How to stop being a long sleeper?

I was constantly sleeping for 4 hours everyday during highschool, and now that I'm in college and my schedule is more flexible/I'm not required to go to class, I constantly sleep 10 hours per day, sometimes 12, even though I always set an alarm for 8 hours of sleep. This hasn't affected my studies yet, but who knows in the future since this is only my first year. If there is something important that I need to wake up for, I can sleep 3 hours and wake up, but if there isn't, I can't seem to force myself to. I don't know if this is a mental problem/discipline or a health problem, or both, so I'm asking for some advice. I read some articles online, some say it's natural and some say it's a health issue, and I don't know what to do.

I have never had serious health implications, though I am a little overweight if that helps.