I would suggest thinking about seeing a psychologist....at the very least you might feel some relief. Quite often if we don't address trauma, it will crop up. Your cousin was well aware that what he was doing was wrong.

It is normal for young children to experiment, but he took advantage of you.....a child.

You might want to write a letter (for yourself) of restorative justice---restorative justice says....this is what you did, this is how it made me feel. I was also molested;sadly it happens so frequently.