Advice on my Girlfriend? Please?

I started talking to this girl two and a half years ago through a friend on msn. We obviously liked eachother but never really mustered up the courage to meet. We chatted for a large majority of the nights. At the start of this year we finally met up and sparks flew. We started going out straight away and it was really cool, she even made my family cookies! But recently, things have started to go a bit strange. She’s been a bit more quiet, and it’s my holidays so I’m full of energy. From this, when I came across a message that she sent a guy friend of hers (he’s gay) telling her how much she loves him, I felt really left out and rejected. Sure, she’s known him her whole life, but I’ve talked to her for nearly three years, I’m her boyfriend and have only achieved about that much too. I got upset and angry at her, I’m not sure if that was unreasonable of me or not. Anyway, this strange vibe i’ve been getting with her is closely linked to her first ual experience (with me) if that-