What does it mean when my boyfriend says he loves spring?

"Spring" here means love, and thinking about spring means being in estrus. It means that he wants to get closer to you and take a step forward in love. To put it bluntly, he wants to have close and distant contact with you. You understand. I think he is pretty good. He is hinting at you and watching your reaction, rather than forcing you to do something. This is a sign of his respect for you. You deserve it. Bless you all and stay safe.