Wife's Sister

My 25 year old wife is pregnant with our first. I love her and never planned on cheating on her, but her sister just turned 18 and I found myself alone with her at my in-laws house a few weeks ago. It didn't take much to get her on her knees, just compliments and telling her I always liked her. She was so eager to please and her body was so much like my wife's used to be. They are Latina with very big breasts and bubble butts but my sister-in-law has a tight little stomach and her breasts are perkier. I was so excited to get her completely naked in front of me and once I was inside her tight high school pu$$y, I couldn't last very long. I slammed her hard and ruined her for anyone her own age. She was louder than my wife and seemed to love it. I came inside her and bought her a plan B.
I haven't gotten the chance to try again but I hope I can keep filling up her tight teen body while my wife is pregnant.