DS1 is 13, had few issues with watching inappropriate videos on utube etc in past. Partly our fault for being blasé about internet filters. Anyway couple of months ago he and friend were sending pictures of boobs/willies etc to each other on Skype that they found on google images. Dealt with that/ told other mum etc.
Now, my son is the class clown - always trying to make people laugh and has a slightly warped sense of humour, a bit risqué for his age shall we say. Tonight caught him on phone in bed so took it off him and looked at text messages . There were a few daft ones he sent today and a few swear words (not great but he's 13)... anyway most horrifying of all he sent a text message to his friend this afternoon which read 'I am having sexual experiences with my mother'. 



Obviously furious asked him about it, says just trying to be funny/ make joke etc.. did not grasp the seriousness of this.
Now worried that friend will show his parents/ teacher etc and SS might come or police 
Also worried about what is going on in sons head to write this!!!!
Help/ advice appreciated 