I'm not sure what went wrong with me.?

I did the same thing! I used to feel so guilty and dirty about it because it was with my cousins and even my own younger sister. I was afraid that when I someday became a mom I was going to do that to my own children like I was some kind of pervert but apparently it's common because we're curious. My youngest cousins are 3 and 1 and I've been alone with them and I've played with them (not in a gross way) and my boyfriend really helped me to realize it was just a normal part of growing up. It is wrong and if you recognize that and are no longer like that then you'll be fine! Talk to someone about it just to get it out there. Trust me you'll be fine and normal.