Hey OP, sending you some sympathy and empathy - my little boy sounds just like yours. He is a bit younger, 7.5 months old, and not crawling yet, but he is the same. Currently does not wanna be held or cuddled, wont sit still on my lap to look at a book or sing a song...he is close to crawling and really wants to spend his whole day writhing around on the floor like a little loon trying to move!!
Please don't worry about it being something you have done, I am sure it is not. He sounds like a lovely, inquisitive, confident little boy who is a testament to how well you are raising him. he will deffo go through more clingy phases as he gets older, and then you will miss these times when you could have a shower without a toddler howling and pulling on the shower curtain!
In the meantime, instead of trying to make him sit on your knee if he's not keen, could you try and find other ways of engaging him? My DS wont sit peacefully on my lap but will roar with laughter if I roll around on the floor with him and have a little game of 'rough and tumble' where I throw him around a bit, blow raspberries on his tummy, tickle him like mad, and generally act like a loon myself
. Can you swoop him up in your arms and play a very knackering physicaly game of peekaboo in a mirror or something? We have a mirror in our hallway and I sometimes play peekaboo with DS by doing sudent squats whilst holding him, so he disappears from view, before practially throwing him up in the hair and yelling 'PEEEEEPOOOOO'....he bloody loves it, the crazy monkey!