I was sexually abused as a kid, and I had the same kinds of thoughts. I would also look out for other things within your childhood. For example, I would roleplay with my dolls and the scenes were often resemblant of sexual abuse (a girl doll would be sick in bed, naked, and the boy doll would be touching her, “taking care of her,” and kissing her).
But really, the main way you will know is the you really do “just know.” Even if you don’t remember it explicitly, your body does. And you’ll know. You’ll have these feelings that you can’t get rid of. Feelings of disgust, feelings of violation. If you are female, you may have some conflict with your femininity (and/or feel like “girls are gross” and “girls are weak”). You may have experienced fear of people similar to the abuser as a small child. You will probably have had very twisted ideas of relationships and sex (I viewed relationships as unequal in regard to power, and sex as a very nonconsensual act throughout my entire childhood).
For me, when I realized what happened, I realized I had known my whole life, but I just didn’t know what to call it. Everything in my life clicked. It all made sense. Even though I don’t have an explicit memory, I know the feeling very well. I can feel the sensory experience (cold air, feeling exposed) whenever I think about it. I have this sick feeling in my stomach, that I have gotten my entire life, which I’ve never been able to explain. When I figured out what happened to me, I instantly knew where that feeling came from.
Then, through discussion with my parents, I actually found out when and who it was.
I really hope you come to a place of closure and understanding about your experiences as a child.