My 16 month old son doesnt say much...?

We have a 16 month old son who doesnt say many words, at least comprehensible words. He says bye bye dada when he leaves for work but it takes a lot of coaxing to get that out of him. He dances, and totally understands what your asking like if you tell him to throw the ball etc. because he does it. I am just worried about his speech I guess. He also doesnt let me read to him as he cant sit still for very long. At his 15 month appointment the doctor didnt seem real concerned and I know there are late talkers and developments but we thought he would be ahead of the curve since he started walking really early (9 months). Anyone else had similar situations or have any learning/teaching resources or techniques they could share?