As pointed out:
1. Stay off these chats.
2. Do not send or receive visual sexual contact.
3. Do not attempt to meet people online who are not adults.
4. If contacted by authorities, refuse to speak to them without an attorney. An attorney will almost certainly tell you to refuse to speak with them period.

As a parent of an (adult) child involved in a child porn investigation, I can tell you that an official investigation will almost certainly come in the form of an action on your ISP for your identity, not some random email or chat message.