Hello everyone, I need some advice on how to deal with this

Hello!
Well before I begin I want to say thank you for reading this and I appreciate any positive/negative comments (that’s why I’m here)
Well my girlfriend and I met in the first year of high school when we were both 15 and 16 and have been together ever since. We have had our ups and downs but none of us every cheated or anything like that. We both live in the USA. Fast-forward to present day, I am 19 and half now and just finished my first year in school in Vancouver (I had to move away from California because I got very good scholarships). We successfully did a year of long distance albeit it was extremely difficult without any of us cheating or anything like that.

Problem is ever since I have been back for summer vacation; I just don’t feel like I am in love with her anymore but I DO love her. She is the sweetest thing I’ve ever met (my first girlfriend) and an amazing girl but I just can’t see myself marrying this girl which makes it difficult for me to give her 100%. During school breaks, I would come down from British Columbia (where I live) to California to my hometown but what makes things even more complicated is that my parents are trying to move to somewhere else which is about 1 hour from my hometown so I will barely get to see my girlfriend.
She is still madly in love with me but lately I have been thinking about breaking off. I catch myself looking at other girls too much, sometimes having fantasies about girls that are not her. She is just not my dream girl and the more we hang out the more I realize we have a lot in common but at the same time; I am starting to realize her flaws more and more.

I haven’t been single in almost 4 years and I feel like I’m already married when I’m only 19! I don’t know what to do anymore the thought of not having her is dreadful but I am not satisfied in my relationship. I have been thinking of breaking up for the past 3 months but I just can bring myself to see her cry 

I am really not sure what to do…I feel like I am not giving her 100% but she is such a good girl that she deserves 10000% but I still love her  Any advice would be GREATLY appreciated  Thank you!!

You still love her, but you're not in love with her anymore?
If you don't want to be in this relationship anymore I believe you should end it and not keep hanging on just because you don't want to hurt her. That's very sweet and kind of you but in time you might start changing your behaviour towards her and end up hurting her anyway. From what you're saying, it's bound to come to an end sooner or later, so it's better to do it now when you can part on good terms.

That feeling of "being in love" is the honeymoon phase of your relationship. It's a mixture of infatuation (crush), lust, and rose-colored glasses. It goes away - always.

The feeling you're left with, the part where you love her - that's the permanent part.

Everything else you're feeling is simply the feeling of being trapped. It happens very easily to young people that have gotten into long-term relationships. You've got to make a choice for yourself - is this truly what you want? If it is, then buckle down and do it. If it isn't, take a break. If you don't know... I'd say hang in there and see what happens.

Break up with her...break ups are never easy. Is it fair to be with someone because you feel sorry for them? is that fair to her? What you are feeling is normal. You are no longer a teenager, you are entering the adult world. You are not the same person 4 years ago, we change, our feelings change, our priorities change and our desires change. You have grown out of this relationship, and you have to ask yourself, do you want to get married any time within the next few years??? NO! so why be with her? Give her the explanation that you need to be free to experience life on your own, and date other people, etc....be honest. She will be heart broken, but she will get over it. Girls are like that, they think a relationship is like a fairytale where you are together forever...NOT! Its ok she will learn, and one day she will be happy that she can go out on her own to be with whomever, flirt with other guys, go clubbing, etc.