Girlfriend is "hiding" our relationship?

[076]

I have been dating my girlfriend for 4 full months. We are 21 years old and study in the same town but live in different.
I was antisocial a lot in the past and had never had a girlfriend. Also I have only 1 best friend and 1 more formal friend with whom I hang out from time to time.
My girlfriend on the other hand had 5-6 boyfriends and a lot of "1 night boys" as she had told me...
I have already introduced her to my bestfriend and they are good friends now, also I plan to introduce her to my 2nd and last friend soon. I even invited her to introduce her to my family but she acted like she was shy, and refused for some reason(I believe its ok since its still too early in our relationship), and I wont push her.
However she has never introduced me to any of her friends, not even her best friend...
So I feel like a stalker when checking her fb wall posts to find out who are her friends with whom she hangs out and who are her ex boyfriends. Found out even that one of her ex's is going out with her when she goes partying without me in her hometown, which made me a bit worried.
Also when I asked for a facebook relationship status(which I don't care about honestly) she said " I don't know after some time"
Why do I feel like she is hiding our relationship?
I don't have any experience with girlfriends but, if you love someone wouldn't you be proud to show and tell the world about that person, and not hide it instead?
At least that's what I feel like and what I am doing.
And i am not sure if even her friends know that she has a boyfriend, maybe they know she is still single..
I just feel like she has a totally sepparate life from me which she is not even trying to include me into.
And yes you would probably tell me to talk to her about it,but.. I am too shy firstly and i wouldnt know even
how to start such a conversation with her?What could i ask her "why wont you introduce me to anyone?"..I dont
want to sound rude and not trust her or push her in any way.
What should I do about this? Am i just being paranoid? Or is she just maybe using me somehow and i am too naive?(i cant believe i even said this)
She is the nicest person i ever had in my life and i dont want to loose her or make her feel bad in any way,
but i just feel too depressed when she goes out drunk in her hometown telling me shes with her friends, and me
having no clue about how much or who are those friends she is with.
Thank you for the answers.

[President]

Jesus

[Veratric]

Tell her upfront that you feel like she's keeping you a secret and want to be introduced to her friends and family. If she refuses or makes excuses, then you should break up with her. This isn't an unreasonable request, there is no good reason she should have to hide you.

But even if you are introduced to her friends, she's still going to go out with them and she's not going to ask your permission first. If that's the real problem, then you are too insecure to be in a relationship at all.

[Elena]

Hi there! English is not my native language so sorry if I had mistake. ( in advanced)
Well when I was 20 yrs old I had bf and I also did what your gf is doing I mean not exactly but almost the same. and I feel bad evertime I remember it. there's a reason behind it and she don't want to introduce you with all her friends because she definitely hiding something and she's lying with you. My advice is confront her talk to her about how you feel and if you think her reason is good enough for you to believe why she's doing such thing then it's all up to you. but do it before you really get hurt or feel like fool and feel bad about it.