what do I do?

Ok so. I'm in a relationship with another female and have been for the last 4 years. Just this past November I became friends with a gay man at work. Recently in the last 4-5months we've become very close as in bestie status 😁 also though, twice now I get into this mood where I'm sexually attracted to him and really I just want to make out with him. I'm certain it has to do with my hormones and the emotional connection I have with him. I'd consider myself to be pan if I were to label. So it's not like it's weird for me to be attracted to a different gender. I just don't understand why I feel this way, and do I tell him? 😱