Best words of encouragement I can offer is that you're not alone with these worries and concerns. There's hundreds and hundreds of people that share these worries. The aggression will be frustration and something that might not last forever. Does he get much help from school or equally as important do you get help from the school?
Schools great, I know it's just because it's half term (he has only just started school) so it's the first time it's changed his new routine. Bizarrely, he is sleeping alright at the minute just I'm not