The chao squirming means it's not happy with the character. Try petting it for a long time to see if that will change anything. Chao mate when they decide to, sometimes it's a long time, sometimes it's often.
In Sonic Adventure 2 DC. My chao somtimes starts squirming in my characters arms. He also always has a frown! Whats wrong? Also, both of my chao are adults so when will they start mating?