This is the problem - the back arching is new so it might just be a new 'thing' that he's learned to do. Head shaking is also something he does when he's tired (has had particularly crap naps today). He is quite sicky today, whereas other days he is not so much...it could all be something, nothing or a mix thereof. Suppose I'll just have to keep worrying an eye on him
E.g. now he is sat in his inflatable nest and has been laughing his head off at me acting like a tit
Miamla he does like Calgel. We have tubes of it all over the house, for those times when you're scrabbling about going 'ffs where's the tooth stuff there there darling, don't cry, bollocks, bollocks, where is it...'