Confused

This is the Third time I told anyone this story mostly because it's very embarrising to me and I'm also very confused about the event. Not sure if it's even considered a trauma because I'm just very confused about it.when I was a child I was about 6 I think,I remember myself being very sexual toward my cousin. He's 15 years older then me. I remember touching him and he would say stop but would be laughing and letting me do it anyway. I was persistent but I don't don't understand why I was doing that. Anyway one day I remember it just being me and and him in the living room and my sister's were in the room watching a movie and I got on top of him and he told me stop but didn't take me off him and basically we almost had sex. Like he was trying to put it in and one of my sister's walked out and I jumped off him and then he just kept calling me bad even to this day. Then after that day I don't remember anything much about him and I still never understood my actions. I thought this event was a dream in a way because I never stop to think about it. I kept trying to forget because I'm 100% embarrassed but I also would like to understand why this happened and why my parents never found out and why he never told. I just don't understand it.im in therapy but I haven't spoken about it because I'm so embarrassed as I mentioned.she asked me if I have any traumas and I told her no since I'm not exactly sure.