Depression and guilt. Towards sister.

I was suffering from ocd when I was 10.and started to develop sexual attraction towards family and would touch my mom inappropriately.later was treated.when I was 14 or15 developed sexual attraction towards sister.i would touch her inappropriately when playing and touched her body when asleep.I would put my hand inside her dress and will feel guilty and stop it.i even did this to my mom twice..but I would forget the entire incident soon..I was very protective of my sister and would fight for her.but I don't know why I did this.i stopped by 16 but did this once or twice later.after all these years I felt guilty and let my mom and sister knew.but they said they were never aware of it and consoled me.but I feel guilty and want to die.i can't imagine what I have done to my sister.she is a year younger than me.the image of putting hands inside my sister s dress is killing me.I grew up without exposure only with my sister and mother.i love my sister and cannot imagine why I did this.pls help