My bad ...
ok look, the best piece of advice has already been given ...
if she says she loves you and you don't feel the same about her, she's not the right one, plain and simple. It doesn't make you weird or fucked up ... or her. When you meet the right person, you'll know it. That being the case, if you're kinda stringing this chick along somehow indirectly given her a reason to think you DO love her or whatever, thats not good for either of you. I'm sure after being with her for several years you at least care about her and her feelings, even if not on a level you would call "love". That being the case, you DO have some level of responsibility towards her feelings. You should talk to her about all of it, with no bullshit. She may want out and if she does, thats probably best for both of you. Even if she doesn't, thats not the best thing but at least you can feel good knowing you put it out there and were 100% honest this way if something does happen and lets say you stumble across some chick that blows your hair back, you've at least begun to clear your path