I'm uncertain about what actions to take.

I'm 16 and this is my first serious relationship, so I'm not an expert in these matters, but I want to share what I'm going through. I've been dating this girl for 10 months, and generally, things have been good. We’ve had minor arguments, but nothing significant. However, recently, I've been grappling with the thought of ending the relationship, and it’s been growing stronger over the past month. Now, it’s all I can think about, and I feel overwhelmed. I’m unsure why I’m feeling this way, and it’s hard to manage. I know it’s not healthy to keep these feelings to myself, and I should probably talk to her about it, but I'm hesitant because I fear it might create bigger problems and could lead to a breakup. At the same time, I feel guilty for not being honest with her, especially since she’s left wondering why I’ve been distant. I'm at a loss for what to do. We spoke today, and she mentioned that I'm acting differently. I told her I love her and apologized for my behavior. Yet, it's not fair to either of us to stay in a relationship if my heart’s not really in it. I feel sick with guilt, haven't eaten much in the past few days, and I'm struggling to find a way forward. I really need some guidance. I would appreciate any honest advice on how to handle this situation. I don't want to be judged or labeled as a terrible person, even though it feels that way right now. I’m just looking for some direction. Thank you for taking the time to read this.