Don't worry - it will pass!!
(I'm no expert but this was my experience anyway)
If I were you, I would follow his lead and allow him to give everything up for the moment - remove all pressure completely. This only has to be a temporary measure - he is still v. young.
My dd (having previously been very gung-ho and up for anything) gave up all her activities at 7 yrs old and just wanted to stay at home. She's also bright and didn't have to try hard at school (bit different now she is older and has gone up a year but that's another story!)
A friend lent me a book called "Your 7 year old - Life in a Minor Key" written by academics from the Gesell Institute of Human Development. (One of a series of book - focusing on children's development - year by year.)
Anyway, I was sceptical because the books are so prescriptive ie at six your child will be behaving like this and at seven like that and I thought dc were all so different and varied in their make-up and behaviour that the books couldn't possibly be accurate.
To cut a long story short, the book described my dd in every detail. To summarise, the seventh year is described as a year of withdrawal, pulling in, calming down. Seven year old children are described as becoming more conscious of themselves as people and how they interact with the world and having many worries and fear that school "will be all too difficult and the things expected may be too hard"
You'll be relieved to hear that it's all change again at 8 yrs (The Gessell Institute book's title for that age is "Your eight year old - lively and outgoing! and so it has proved to be.) We took all pressure off our dd at 7yrs and didn't insist that she went to activities or did anything much other than play with friends every so often. She's gradually gone back to extra-curricular classes (not too many) and seems to be enjoying herself again.
Homework is a different story though! 