Please help...

Okay so first of all, I'm a good girl who has only had sex with my boyfriend of 3 and a half years. He's my first boyfriend and I would NEVER do anything to hurt him and cheating on him is way out of my moral code. However, college is hard and it's put a lot of stress on our relationship and he doesn't do much to make me feel "special" or "wanted" and I definitely don't come first because school and him wanting to be a doctor comes first. I have a friend who, from the moment I met him, I've felt connected to. It's the kind of connection where just seeing him from across a room makes me smile uncontrollably and gives me butterflies. He, like me, is a very sexual charged individual. He's told me how beautiful he thinks I am and how I deserve to feel appreciated and whatnot. The downside is...he's married. It isn't a strong marriage by any means, but he's still married. Everything inside me is telling me to run...but part of me still wants it. I don't know what to do and it's driving me crazy. Please help.
P.s. Literally crying while typing this so any help is appreciated. Thanks.