How do I (17M) tell my girlfriend (16F) that I'm losing feelings for her?

It's been 4 months since me (17M) and my girlfriend (17F) started dating and I've started to lose feelings for her recently in which I'd say about 2 weeks. Yes, I know it sounds shitty. I want to tell her but I don't know how to because she's a nice girl and I can't stand the thought of hurting her feelings. How do I tell her in the least hurtful way? I'm pretty new to relationships so I'm not sure what to do.