(I know that we're young and we have plenty of time left in our life blah blah blah..)

Hi! 
So like the title says : I'm completely lost in my relationship..
I've been with my girlfriend for one year and a half now and I don't not what is the next step or what to do now. I love her and since our very first sight we knew that we were made to be together but now, after all that time, I think that my 18 y/o mindset is coming back.. 
Since we are together, I stopped going out/partying and now every day and week-end we are together and all that for more than a year now! 
Now I think I went to move on but the thing is that I still love her and we are happy when we are together but I want try something (somebody) else... Does that make me an asshole?
She is young, very young... and because of that, I don't know how or if I should end our relationship. If I do it, it will be so brutal/rough for her because she is that young. She loves me like no other girl ever loved me and it is the same for me.
What can I do? Help me..
PS: I'm french.. I tried my best for my English to look good.
PS²: If you're wondering, we have sex a LOT and it's all great so that's not the problem (I know about statutory rape, etc.. Her parents and mine are ok with that. )
user
My relationship
assistant
(I know that we're young and we have plenty of time left in our life blah blah blah..)

Hi! 
So like the title says : I'm completely lost in my relationship..
I've been with my girlfriend for one year and a half now and I don't not what is the next step or what to do now. I love her and since our very first sight we knew that we were made to be together but now, after all that time, I think that my 18 y/o mindset is coming back.. 
Since we are together, I stopped going out/partying and now every day and week-end we are together and all that for more than a year now! 
Now I think I went to move on but the thing is that I still love her and we are happy when we are together but I want try something (somebody) else... Does that make me an asshole?
She is young, very young... and because of that, I don't know how or if I should end our relationship. If I do it, it will be so brutal/rough for her because she is that young. She loves me like no other girl ever loved me and it is the same for me.
What can I do? Help me..
PS: I'm french.. I tried my best for my English to look good.
PS²: If you're wondering, we have sex a LOT and it's all great so that's not the problem (I know about statutory rape, etc.. Her parents and mine are ok with that. )
user
I'm completely
assistant