What should I do about this?

About a month ago, I was talking to a dominatrix online. Yeah, I'm into that. One problem is, I'm only sixteen. I lie and tell people I'm eighteen. My photos p off for being eighteen. Anyway, this girl told me to go get my mom's underwear and put them in my mouth. I thought about it for a while, but eventually decided I would do it. My mom was in her room, though, so I went into my sister's room and got a pair of hers. I thought the dominatrix wouldn't know the difference. So anyway I put them in my mouth, like wholly. I knew it was a bad idea, but I did it anyway. It didn't hit me, what I had done, until like three or four days later. Ever since then, I've been obsessing about it. I have OCD, so that definitely makes it worse. I've been obsessing about it because it feels like I committed or something.