Why is my girlfriend so secretive when she's near me? Is it me?

Okay, so I have a situation where I can hardly ever communicate with my girlfriend anymore.

I’ve been with my girlfriend for almost 2 years now, and recently, I feel like she’s been keeping things from me. When we started going out, we always told each other everything, even our secrets. It all seemed like a great relationship filled with trust.

About 3-4 months ago, I randomly took a peek at her a social site profile and found this list of friends who were majority of guys. I confront her and she tells me it’s just people she added. No big deal for me. What was a big deal was that she went and hung out with those people and never even told me about it. I waited for more than 7 hours for her. I was upset, but I didn’t want her to feel bad.

A few weeks later, I learn from her friends that she’s been having some trouble with work and family(family owned store). I told her that there was something her friends told me about the store and family and she got really mad. I apologized, but she kept on going how I’m always in her face, and how I annoy her all the time. Being upset, I just told her “I’ll go away then..” and I left.

We’ve been having these fights so much now. I feel like it’s me. Why is she getting mad? Why does she hide this from me? What should I do to make her better? It’s almost our 2 year anniversary(Feb.) and I really want her happy, also need a gift too. Is there anyone who can answer these questions for me? Thanks.