This is why August is my least favorite month

I don't know if my story is as traumatizing as others, but I have to share. I was between the ages of 5 to 10. My parents split when I was about 4, so half the summer I spend with my dad. We always went on a 2 week vacation to Spain. Just me, my brother(then sister), my dad and his best friend. His best friend is called Raymond. I only saw him once or twice a year, and always dreaded the day I would be seeing him again. In the pool, he'd always pick us up even though we were not comfortable with him doing that. He always stared at us, especially when I wore my swimming clothes or when I pulled off my shirt because it was too hot. I didn't understand it back then, but it felt wrong. I hated Raymond. He never gave me the privacy I needed and I didn't want to be alone with him. I told my dad, but he doesn't understand. He made excuses as to why Raymond was acting that way. The final straw happened when me and my brother were about 10. We were both in the bathroom taking a bath, and Raymond barged in and pulled the curtain away. I don't remember what happened next, just that I screamed. My dad always said after the bath incident, as I call it, he made sure to keep Raymond away from us. But he failed to protect me as a kid and I can never forgive him for that. My relationship with my dad is not good because this still lingers in my mind. I am almost 20 years old now. For more then ten years I couldn't look at myself. I have my first boyfriend now, and this experience is in the way between intimate activities often. I still feel disgusted by myself often. I don't want anyone to look at me sexually, sometimes not even my own boyfriend. I wish my dad had protected me like a good father. And I wish he would believe me.