My Secret with My Graduate Student

I'm a first-year law student but I play daddy in an adult relationship with my graduate assistant who is four years younger. We never discuss her age or mine, just that she's the little girl and I'm the strict daddy figure. Our sessions are intense, lots of spanking, verbal humiliation, and roleplay where I have absolute control over what we do. She loves when I give her assignments to earn my approval, like writing a paper on my terms with specific words and phrases in it that make me feel dominant. But honestly? The hardest part is the physical intimacy. We strip each other naked, sometimes I tie her up for a scene where she's completely at my mercy. It leaves me feeling ashamed because deep down I know this isn't normal or healthy. She gets off on being told what to do and I get off punishing her in return. And yet when we're alone together? There's always that nagging guilt weighing heavy on my heart.