Thank you very much for the replies. I was not quite detailed about the whole thing, and I am still articulating, or trying to ,what is going on in front of my eyes.
So in brief - it started all very sudden. In mid- December, with not wanting to eat the food because someone coughed on it, Christmas was not a happy event, eventually he moved to a separate room to eat. Things got slightly worse in January, started to wash his hands, but I still did not feel that I needed to seek medical help urgently. He was otherwise OK. However, last Tuesday everything just went out of control. It feels like a watershed moment.(The previous Friday, he started that he wanted I bath, I could not take him to school, husband came back and took him). Spent 3 days at home (was sent home because he was unwell, chesty cough is circulating around), and by the weekend he was not only wanted the bath etc but became extremely aggressive just out of the blue.
So this is this aggression, which I feel is more than OCD related one.
And up to last weekend he played beautifully with his siblings. (We are quite isolated,no playmates (probably partly because I am not quite integrated here, my husband is British but I am not), so I always thought that how good that my children are quite close to each other in terms of age and emotionally as well, so they still have someone to play with. So that what it was before. So he was a normal child, his aggression was normal (I could see reasons why he did things when he did.) As opposed to now, when he just lost some inner control of himself. Throwing bottles, milk pouring out, food thrown everywhere, apples throw at his sister, shoes thrown at me. And no remorse, not feeling embarrassed about it or anything. And lots of them just unprovoked. And then a couple of minutes after he is smiling again and quite nicely ask me to do something for him.
It feels that he just went mad. I do not understand his behaviour. I think it might be something on top of the OCD symptoms. (I mentioned PANDA/PANS to the GP, he dismissed the idea.) Any idea of this?
About CBT therapy. Thank you again for the advice of looking it a bit more broadly to start with. So I looked at the Portland Hospital in London, for a paediatrician specialised in neurodevelopment. The health visitor recommended that I go back to the GP (to a different one) and discuss with him where to start. Paediatritian? Psychologyst? I am not quite sure.
Any experience would be welcomed how the OCD came on, was it a sudden thing, or something more slow? I even do not know what quick means.
I try to post later about the school a little. (I can!t even decide whether it is a good idea to take him to school or not, let him have a bath before or not.)
Anyway, thank you for reading it. And thanks for the replies too.