Extremely depressed?

Ever since i started dating her i have times when i get really depressed.....i feel like she's controlling. I can't leave her because im in love with her. I lose interest in things i like too....She takes me away from what i love, basketball. She makes me choose over her or bball sometimes. Wouldnt someone who loves me understand or care? someone times i punch myself or self inflict pain...what do i do. i dont wanna be like this.