Can a person fall back in love?

My boyfriend and I have been together almost 2 years, and we're planning to move in together, with talks of a future, marriage, and kids. Recently, I've been busy with work and school, and he's been visiting his cousin on weekends. This distance has caused us to grow apart, and he’s been struggling with his mental health, which has made him feel less "in love" with me. We’ve had our share of bickering, and he’s unsure if we’re meant to be, given his emotional state. He’s thinking about breaking up, but we’ve agreed to take time to work on things before making any decisions. We had a good day together recently, so I know we’re both trying.

This is my first long-term relationship, and I’d love any advice or perspective on whether we can rebuild or if the relationship is beyond repair.