I'm 19 I get really bad tooth aches. I really don't think I could have that many cavities, so is it something else?

Could be. It mightvbe something else, but see your dentist to rule out cavities first.
Possibly. It can easily be cavities, your age has nothing to do with it, we have seen even 3 year olds with multiple cavities. It can also be due to trauma such as tooth grinding or clenching, or some type of other factor such as compression on the nerves that run to your teeth such as a sinus infection.
Yes. Anything from trauma to gum disease to wisdom teeth to neoplasms and so may more reasons. Don't try to diagnose yourself. You don't have the training or the experience. There's good and just reasons for regular Dental care. Call your Dentist before you're dealing with a painful emergency.
See your dentist. How often do you go to the dentist? I have had to take out many teeth in teenagers because they didn't take really good care of them. Made dentures for a 22 yr old before. Also look into your wisdom teeth if they haven't been removed.