Help I just had with my stepmom an now shes pregent?

Ok the story goes like this I was alone with my stepmom watching tv when my dad called and said that he couldnt ome home he had a busness trip so my stepmom got mad and starting to drink all his beer and she got drunk and started saying that he was cheating on him and she was going to cheat on him so she looked at me and took of her top and said **** me and I thought yes becaues shes hot but a few weeks went by and she missed her period she hasn't told my dad yet because he had a vesticamy what should I do?