I think I actually have very strong feelings for my girlfriend.
That is great, have you told her about it?
I have not told her I love her yet.
It's nice that you think you love your gf. She'd be happy if you told her.
I never told her. I don't want to ruin our relationship.
I think you should tell her. It is only right to be truthful to your girlfriend in this scenario. She may already know, and is just waiting for you to vocalize it.