Disclaimer: Newbie

So to put things into perspective, I'm a 20 year old guy who's been lurking TRP for some months now. Have a almost 2 year LTR with this girl, 3 years my senior, whom I met in college when I was 18. She fell for the tough guy persona I had created to avoid being hurt. To be honest, I only asked her because she had already had given me a handjob in her car once and I was desperate and tired of being a virgin (yeah, I know).

We lost our virginity together, but I was (am?) so insecure about it I told her I had done it before. Apparently I performed adequately (yay, goal accomplished?).

I had gone out and made out with girls at parties before, but this was my first experience with a "serious" relationship.

As the months went by I discovered the slew of problems my girlfriend had (a tough upbringing to summarize it), which led to her being really insecure and prone to jealousy.

If her words and acts are to be trusted, apparently she means it when she says she loves me, and likes to talk about us moving in together, getting married and having children, even though I always divert the conversation elsewhere as I believe I'm way too young to be committed like that.

In the meantime, I continued college and got a nice full-time job.

There's this girl, about my age, at work (spare me the don't shit where you eat lecture), we work in different departments, but I happen to pass by where she works everyday. A smile here, a wink there, a brushing hand there, and I developed a huge crush on her(I know). To the point where I'm scheduled to compete at a sports event this weekend, and my gf's coming to watch me. But in my mind I saw this girl, her smile, her long flowing silky hair, cheering for me. I've talked to her sometimes and I think she's attracted to me too. To be honest, she's really forward with it (that's kind of normal in my culture).

I realized all the things I was "supposed" to feel with my girlfriend, whom I "love", I felt whenever I saw this girl. I've never felt like that before (I know).

We were talking today as usual, when one of her colleagues (also female) asked me if I had a girlfriend. This caught me off-guard, and my brain rapidly went into overdrive, and I responded by making the so-so gesture with my head, saying "More or less", and smiling.

The girl smiled and said "you should have told me sooner, and I wouldn't have gotten my hopes up". I laughed, teased her a little and went back to my cubicle.

When I left, I stopped by her cubicle to talk a bit. I didn't notice anything different on her behavior, but I was a bit anxious, so I may have misinterpreted something.

My question is: how to proceed from here?

I've been thinking for some time I should break up with my girlfriend, but I'm not really sure how.

Also, with this other girl, did I fuck everything up? How should I proceed?