I don't love my girlfriend anymore (complicated)?

Our relationship hasnt been going that long only about 4 months and I already feel its getting old and time to break up. She is a really nice girl and should be perfect for me but i feel that shes more like my best friend than my girlfriend but she absolutely adores and loves me. Im nice to her and I listen to everything she says and I even take care of her when shes feeling ill (quite often) but I really dont want to bee in a relationship anymore. This time last year I was with another girl who was my first "serious" relationship, we where together about five months and i loved her with all my heart even though out relationship was long distance and not the best, when she dumped me I went into almost chronic depression for about 2 months but a week after she dumped me i got myself a rebound who i hated after a month and this made me sick of relationships... 5 months later I get with this "perfect" girl who I thought should be everything I ever wanted but she just copies everything I do and idolises me like a child would their parents, the worst part is shes 2 years older than me. I know i should love this girl any way but I cant. everything she does annoys me and she tries to live up to the lifestyle I want to live but my lifes become boring and mundane as she wants to see me every waking hour god gives. If I dump her shell be so hurt but if we continue then our lives will just become worthless and trashy. Im 16 and were already acting like old hermits in a retirement home. Shes a lovely girl but she has no real friends and im all shes got and dumping her would take away everything she has and im afraid there will be noone there to help her if i do. we have loads in common but she always gets annoyed when I say anything about her being feminine or girly so she really makes me uncomfortable. Id love her as a best friend but I cant take this monotony anymore. plus I still havnt got over that one girl that broke my heart.. or i could just man up and stop wallowing in my sorrows haha but seriously I need help on this, I care about her feelings i really do but this relationship is pointless. please help.