Fucked up "love"?

I'm confused. I've been with my girlfriend for over a year, and we've sworn to forever. At one point I did love her with all my heart. She was the world to me. She was my everything, and just the thought of losing her scared me shitless. I would have done anything for her. I don't know. Over the year a whole lot of shit happened. Broken friendships, coming out to my family and their reaction to my girlfriend and I, grandpa being hospitalized and dad having to go back home just in case he doesn't make it, dad drinking too much over the years to the point where his skin was turning yellow from the liver failure, and him being taken to the hospital by ambulance in the middle of the night because he was puking blood, finding out he has cancer, him having to have surgery, and now he has to go through chemotherapy sessions. My life up until now has been plain, simple, easy. Nothing bad had ever happened to me before. I was a happy kid. And when I fell in love with her I was even happier. I actually believed that life could be perfect. My heart swelled with love and happiness. But after this year, I feel broken. I'm not completely dead, but it really isn't the same anymore. I cry randomly. I've cut. I've started smoking. And I have these terrible mood swings and treat my girlfriend like shit. But she puts up with all of that, my destructiveness and my attitude. She loves me and cares about me and she was my only light of hope during all the mess. Yet, I'm at the point right now where I don't know how I feel about anything. It's as if I'm dead. I don't care. I don't feel happy. When I do feel it tends to be negative. Sadness and anger. I don't know, it's scary. I feel like none of my friends are worth it anymore. I feel lost. I don't know what to do with my life. The future I had roughly planned out isn't working for me, and I don't know what to do. I have no goals or dreams. I feel like a failure. But I wouldn't mind all of this if it weren't for the one other thing that comes with this "feelinglessness". It's that I don't feel like I love her anymore. Before, when we'd cuddle and just stare into each others eyes or kiss or hug, I'd feel something. I'd feel happiness inside. I'd feel this smile grow on my face naturally. And now it's as if nothing's there anymore. When we do all the stuff that used to reassure me that I loved her, I don't feel anything. I just go through the action, my mind elsewhere. I can't tell if it's just because I'm like this right now, or if I really don't love her anymore. And it scares the shit out of me. I've talked to her about this and I don't think I'd want to lose her. It would just be strange if she weren't there in my life. I don't know. Is it even possible to not love her anymore but still want to be with her? Because even though I feel like none of my friends are worth it, she's the exception. I'd want to keep her in my life. At least I think I do. What's wrong with me? And what should I do about it? Am I messed up?