Is it normal i had sex with my mothers girlfriend?

Is it normal? One day, I was in my moms room changing for my friends party when I heard the door open and it was my mom. She did not know I was changing at the time so she just walked in. She looked at me sexually because I only had my panties on. My mom is now a lesbian so she got turned on. She was my moms girlfriend and I think she is smoking hot. I ran to the bedroom door and locked it. After this I plunged at my moms girlfriend trying to kiss her. I was so horny that I didnt know what I was doing. I took my panties of and then undressed her. I was feeling a bit mean because she just lay there doing nothing. I couldnt get enough so I started to finger her until she came. She wasn't groaning or getting any pleasure. I felt as if I was doing everything (which was happening). I was begging her to please me. So she then started to kiss me and rub my tit. After those five minutes of love i came all over my outfit and over her. After, I then realised that this was unfair to my mother and her girlfriend, so i got dressed. There was no way of me going to the party now so we sat down and talked about it. My mother was not allarmed by this and neither was her girlfriend. I am now a year older and things are just how they should be.