Torn between Two

Six years ago, I fell in love with this girl at first sight.

I was after for 3 years before she started going out with someone else...

During my down period, this girl came into my life, she was EVERYTHING a guy can ask for and loved me deeply without hesitation...we now have been together for three years...

During those three years, I kept in touch with the girl that I first fell in love with, and she revealed a while back that she did love me, but was afraid that we were too different to be together and she might hurt me by accident...

Recently, we've been contacting a lot...and I'm now emotionally confused...

I love my current girlfriend...but I also love my first love...

My girlfriend have 99% of my heart, yet, that 1% that I kept for my first love is like a burning fire...

I want to face my true feelings, but I know that if I do, I will really hurt my girlfriend, but if I don't tell her about it, it's unfair for her...

What should I do?

To tell or not tell?