what do you think?

I need outside opinions in this situation. I am currently away on a long weekend for a bachelorette party. I'm still nursing so no drinking for me. I am here to support the bride but my heart and head are at home with my 7.5 month old. My fiancé is supposed to be with the baby with help from both of our mother. He works late and leaves early in the am 7 days a week so he's tires, understandably so. My sister is also here so my mother is watching my niece over the weekend. He dropped my daughter off with my mother because he was tired and needed to catch up on sleep. I tracked his location to find at 1 am that he is at a club, unbeknownst to me. I am seething with anger at this selfish behavior. Am I overreacting?