My rule is that it's fine as long as it's not interfering with your life. Do you skip school, have trouble working, have difficulty focusing because of your partying and drinking? If things are ending up not so great when you drink, then you may be overdoing it. Drinking can be a kind of unhealthy self-medicating.

Hypersexual activity is a classic sign of mania, so that may be something to monitor. If you just have a high sex drive, you just have a high sex drive, but you should pay attention to changes to it as that's a signal something's wrong.

Basically, just look at your behavior and see if it's negatively impacting your life. If not, then just enjoy your early 20s and be safe.