I would generally use the standard precautions (VPN/Tor/etc.) but I think these organizations would much rather have you report the content than go after you, unless you've been reporting a suspicious amount of content that indicates you frequent such circles (i.e. you're one of those internet vigilantes).

Both of the reporting tools I linked allow fully anonymous reports.

If you are consuming or encountering CSAM in a fashion where it is not clear that you are not seeking it out and participating in its acquisition and distribution I suggest that you seek both medical and legal help.