I have a friend who has your problem, but much, much worse. He did a sleep study once to figure out what was going wrong, where they hooked up electrodes to his head to monitor his sleep stages through the night. He woke up, on average, every 8 minutes.

There are a couple things that can cause this. First, if you're overweight or often drunk when you go to sleep, you might have apnea. Apnea happens when your throat closes while you're asleep, and you can't breathe. After several seconds, your body panics, and you wake up very briefly, adjust your position, and go back to sleep. Then it happens again in a few minutes to an hour. Apnea is typically accompanied by loud snoring. If you develop apnea at 21, you need to lose weight or stop drinking so much.

Another possibility is just that you have poor sleep hygiene, and it's catching up with you as you get older. This means you go to bed and get up and different times on different days, so your body doesn't have a consistent schedule.

Sleeping pills are a temporary solution. They will eventually stop working, and you'll be in even worse shape than you started. Google "sleep hygiene" for a lot of information about how you can train your body to sleep properly.