Hooking up with my best friend

Let’s start by saying I’m a very introverted sexual person, meaning I’m shy, afraid of rejection and love sex… I’ve been in a relationship with a guy for 2 years and my best friend is married, however we both hook up every now and then.. mostly when we are drinking. Both our significant others know and are ok with it… but she always initiates because I can’t read her. Its so much fun and it’s incredibly sexy, it’s also just that, fun and sex.. we’ve never talked about it but we are both in agreement that it’s just for fun….It’s been a few months since the last time and I’m dying to fxck her….