But how do I stop acting like a teenager when I'm 23? btw,
they seemed ok with it and even think it's funny, but I just wanna stop period.
Well, it's good that at 23 you've decided to start acting like the adult that you are.
Do you want your boss and your co-workers to think you're that ditzy chick that they think is funny (because she acts like a kid), or do you want to be treated with respect, and as an equal?
Could be that until this time you've always gotten what you want, or got attention by acting cutsy and carefree. Perhaps it's time to wean yourself off of that.
How do you stop? The way others have said, start acting like the professional people around you. That's not saying you have to be boring, but you need to realize there's a time and a place for acting all LOL.
Many people who work together will occassionally go out for a drink after work, but this is not partying. If they are in their 30's, chances are they have families, or other interests which don't include going out to bars often.