CURIOUS

so my bf of 10 months has asked me 3 times since we've been together "why do I love him"? I give him soo many reasons: he's personality , hes a great father, provider , because he loves me unconditionally despite my mood swings etc..BUT he says he looking for 1 specific answer that I haven't mentioned. I gave him my reasons why I love him but he's looking for 1 answer. I'm getting frustrated because I feel like he has doubts that I love him. what am I missing here??