Ask the doctor if it concerns you, trust your instinct. But like everyone said, it could just be normal for him. If he can follow commands then he can understand words, and he hears even quiet noises, so I doubt it's his ears, but of course I'm not a doctor.
My son just turned 2 three months ago, and is having a vocabulary explosion lately. He points at and names everything he recognizes on TV or in a book, but still not everyone can understand all his words. And he has just started making small sentences, like "Vinny go night night" or "get outta here" to the dog. Prior to this he had some clearly understood words he said a lot and a mix of words only family can understand mixed with grunts and pointing at what he wants.
He is very active and rambunctious and I also always kind of thought that he was just to busy to be bothered with trying to say the words right. He has a cousin 1 month younger than him who is speaking long, clear sentences and has a ton of words since before she even turned 2. But then she's been ahead in everything, like walking at 9 months when my son didn't walk until his 1st birthday.
Best of luck with everything, and keep us updated on what the doctor says. But try not to worry too much, because it could just be completely normal.
P.S. I just had to add that he seriously looks like a little angel in that picture! Don't you just love how peaceful they look when they're sleeping?
