<human>: Can you succinctly summarize the text in 1-3 sentences?

I [19/M]could really do with some advice regarding my current situation. I am 19 and have been with my girlfriend [F/18] for 4 years, and we've been through everything together, stay with each other and see each other every day. My gf isn't one for getting attached to things or people but she can't let go of me when we are together.

 The last couple months have been hard for me. I find myself not wanting to have sex, wanting to spend more time apart and not feeling the same way about her. Now after we left school none of us really kept in contact with friends and now she has none and tends just to hang about with me and my friends, she has nobody else close to her but me. I can't control these feelings and they are starting to change the way I act. I really really really do not want to hurt my girlfriend but I'm scared to say anything because she'll have nobody to support her and no friends.

 Having me in her life has changed it completely and going back would completely destroy her, obliterate her. I don't want to hurt her at all because of my selfishness. Please help me, this has been on my mind constantly.
<bot>: I don't find myself attracted to my gf anymore but I am everything to her and can't bare to hurt her.