Is there something wrong with my kitten mentally?

I have a kitten who just turned 10 weeks. I got him when he was 6 weeks. The previous owner told me that the mama cat dropped him off the bed onto the floor when he was still a wee baby. He's absolutely gorgeous and would steal your heart away and I love him regardless but I need to know if anyone has had this happen to their kittens. He still doesn't know how to purr. He's very calm and playful and loves to be held. However, he doesn't walk properly. He kinda wobbles side to side and his legs are always so stiff. He can't jump without his back legs freezing and then tipping over on his side or back. He runs into things and he actually knocked himself out for a minute once when he ran into the gl shelf. The other day I was vacuuming the house and my other kitty ran off to hide but he froze in place. His legs froze in place and he fell over to his side and couldn't run. Please help? What do you think? a href="http://i2.photobucket.com/albums/y10/swt_ly/Icosleepstanding.jpg" rel="nofollow"http://i2.photobucket.com/albums/y10/swt…/a