What to Do?

I've been with my girlfriend for 3 1/2 years. We entered the relationship for fun and companionship and there were no real feelings there, at least for me. After a while we decided that we both wanted to stay together and work on things due to common goals. But it seems to me that the whole relationship was one of convinience. We are great friends, business partners, bed-buddies, and want the same things in our lives. We rely on each other.

Recently I spent some time away from her and when she came back I got nasty stomach cramps around her. When I go out meet new people and see friends they go away. They are usually always around her. I respect, care and give her everything in me to give but I don't know if the love is there or if fear is keeping us together. I guess I've been hoping all this time that the love would come on it's own. But it hasn't. How do you tell your best friend and partner this? I feel like all I do is lie to myself that this will work and I want it to work. I am really stubborn but scared. But I feel that she is lying to herself too.

I moved in with her because my parents were making me angry and I needed somewhere to escape. They were bothering me because of her. So I left.

Two weeks ago a friend of mine told me I wasn't in love and I told this to my girlfriend, that it might be true. She freaked out and said she wanted to get engaged right away. I said yes but backed away two days later. I feel that neither of us wants to be the one to break the relationship off. Were both afraid of regrets. I've pissed her off to no end and she won't leave. She tells me that I should stay. I am sooooooo confused.