I think boys develop speech at a slower rate than girls.
DS is 19 months, he has said plently of words, I have only heard some of them once then not again for months. He babbles and has lots of baby talk, and is very good with his body language. I only think he had a handful of words at 12 months. Some books say they should have about 50 words by 18 months and 100 by 24 months.
I wouldn't be too worried just yet.