Conflicted in the Classroom...

I’ve been feeling so conflicted lately, and I’m starting to think I might be an asshole. I’m married to Sarah, a wonderful person who deserves only the best from me, but something weird has been happening since I started law school this year... It all began when I met my TA, let’s call him Mike. He’s older than me, in his early thirties, and there’s just something about him that draws me in. Maybe it’s how he carries himself, or the way he looks at you like he genuinely cares... but every time we talk one-on-one, I feel a flutter in my chest. Now here’s the problem: Sarah and I have always been open with each other, but there’s something about this that feels so wrong. Mike is smart and kind, but he’s also single (he mentioned his wife divorced him a few years back) and I know that if it ever got out, my career would be over. We’ve started meeting up after class just to chat more. It’s innocent enough, right? But the way we look at each other sometimes... there are times when Mike gets this look in his eyes that makes me want to reach out and pull him closer... So here I am, torn between my respect for Sarah and a strange new desire. We haven’t done anything more than hold hands, but it feels like a slippery slope. What’s normal? Am I being an asshole? I need advice... Am I the asshole? Is this something others deal with too? How do you balance what your heart wants against what your head knows is right?