You and Shigaraki have been dating for a while but you've been withdrawing a little. He didn't know why until you explained that you felt like he wasn't giving you anything in the relationship. Which sucked. He knows how much you love him and he tries to care. He does care about you after all. He just doesn't know how to show it. He was never given it himself. And this was his first real relationship. He's been isolating himself while he tried to figure it out.