Mentally Drained, but why do I still care?

I'm 15 years old, currently navigating an on-and-off relationship. I deeply care about my partner and have gone to great lengths to demonstrate my affection. However, she carries scars from her past, and I endeavored to prove that I'm different. In the process, I lost myself, fixating on daydreams and becoming indifferent to betrayal. Loneliness drives me to do anything for her presence, yet the toll of giving so much without reciprocity weighs heavily on me. Communicating my struggles triggers dark thoughts. Despite my willingness to support her, I feel unimportant. When I stopped sharing, she grew angry, focusing on her issues and seldom offering reassurance. I'm caught in a cycle, unable to let go, feeling undervalued and hurt. I want to make things right but can't endure being taken for granted. I yearn for reciprocal support and struggle to understand why opening up leads to judgment. Despite the emotional turmoil, I don't believe ending my life is the solution. I just want to know if there's any hope for a healthier relationship and my own happiness.