Unsure of which direction to take!

Hey guys, Basically I have been with my girlfriend for almost 3 years and she is fantastic, loving, caring and always there for me. However I feel as though I am developing more as a person and beginning to grow up faster than she is. To give you some background we are both 19 turning 20 soon and we work together (although our employer employees about 2000 people) and go to university together as well. She means so much to me and most of the time I cant imagine a life without her but recently I have been having second thoughts. We both used to be very clingy and worry about each other significantly but as time has gone past I feel as though I have matured and she has not in this regard. I feel comfortable letting her do her own thing but she doesn't really want to spend time away from me, she gets angry when I want to have a shower and doesn't like me going to the gym etc etc. I also have been making new male friends and trying to hang out with them and I really feel as though she is frustrated by me doing this. I love her and she is beautiful in every way but I want some sort of independence now, I actually feel as though im suffocating a little bit and want some time to myself to be with my own person. However I am scared if I break up with her that I will regret it majorly, break her heart and be miserable for the rest of my life :(. I also haven't really been with any other women and that does play on my mind from time to time. I should also note that im a pretty good looking guy, but she is a stunning girl so I guess I am doing pretty well for myself. Am I being selfish in wanting to have more time to myself? Do I not love her for wanting to not spend every moment with her? Maybe this is the reason relationships commencing so young often don't last forever! I really need some advice because im unsure of what to do and am getting frustrated with the way things are. I also really don't think she would take it well if I brought these things up. Thanks for your help guys!

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