Unfortunately it takes two people for a relationship to work and move forward. No matter how much you care about somebody, it doesn't matter a thing if they aren't able to reciprocate it. While she felt like she loved you before, she doesn't feel that feeling anymore. We change our mind all the time, and our feelings change all the time. Not to mention she may be looking at other people but she tried to spare your feelings. But no matter what the reason, whether you did anything wrong or not, the result is the same: she doesn't feel that way anymore.
So what can you do? Instead of focusing on her and how to get her back, focus on you and how you can make yourself happy? Are there some hobbies you had that you kind of let up when you spent more time with your girlfriend? Get back into those. Same with friends, start spending more time with them and rebuilding the friendships that probably suffered when you spent alot of time with her. Going to the gym and getting in shape will make you feel better about yourself. Concentrating on work and getting a promotion, or on school to help better yourself career-wise is not a bad move either. Basically, it's about improving you and making you a better person coming out of this relationship. It hurts, and you are going to think about her all the time, but what are you going to do? The longer you keep focusing on her, the harder it is going to hurt and it's going to kill you when she has a new boyfriend (which she will), although for me that was what helped me kill any thoughts of us getting back together.
You have to ask yourself: will this honestly help me feel better? If it does, then you do it. I say this for situations like when you check her facebook? Does checking it make you feel better? Does it hurt and make you cry? If so, why do it? You have to exercise yourself some self control. Hide her stories in your minifeed, and her best friends too because they will write on her wall and all that shabang. You are really in complete control of checking it, so don't do it. You don't want to have to delete her and then have to crawl back again when you realize that you don't mind having her as a friend or who knows what could happen in the future. But it's out of your hands. Take a deep breath, focus on yourself, and when you finally find happiness within, you will realize that you don't need her in your life to be happy. You will find somebody that will increase your happiness after. I promise.
It takes alot of hard work and you have to keep yourself focused every day. You will hit those ups and downs. But it will get better and your attachment to her will fade as long as you don't keep in contact with her. Funny how when you stop chasing her, she'll find a way to pop up back in your life. And then you can decide from there if you are better off on your own without somebody that would treat you like this and break your heart. We'll cross that bridge when we come to it.
One step at a time. Everything will be okay no matter how it works out.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.