I've slept with over 300 guys and am a 21-year-old female.
Whoa, that's quite a lot. Did something I say remind you of sleeping with those guys?
No, I just thought about it.
Sleeping with so many people is a risk to your health. You could get a disease or pregnant.
It's okay since I get myself tested and use condoms.
Sleeping with that many people can be a serious risk because if you were to contract a disease it wouldn't be only a risk to yourself but a risk to however many partners you've slept with since contracting it.  If you are responsible and practice safe sex there isn't anything truly wrong with having many partners, however you should know the risk increases each time that something may go wrong.