I caught my stepmom masturbating, but why am I so turned on?

Ok, so I got in my parents room right. And what do I see? My stepmom is laying naked on bed rubbing her fluffy pussy! I can't believe I caught my stepmom masturbating! But instead of being shocked, I had this little tinkle down there... So I thought I'd do the ballsy thing: I asked her why she was masturbating and proposed her to help her out if she needed a little help. My stepmom is sooo hot with her nice big natural boobs and her fluffy pussy that I just couldn't resist and kissed her on the lips. Well, you know. One thing led to another and before I knew it I was having a full on session with her. She definitely is a great teacher and now I want more!