I was once told that receptive language should be counted as language development too. So, does he understand things you say? Can you give him small direction like “give mama the ball” and he does it? Some are late talkers, but are still understanding words. Are you teaching body parts? My kids were all late talkers, but my docs said not to worry because of their receptive language. You’re doing the right thing by getting him checked out. That’s all you can do right now! You’re doing great!
It sounds like he understands things so I wouldn't worry too much. Some kids won't talk if they can communicate just fine another way.
He understands most of what we say to him. His comprehension seems quite good, he just won’t make vocalizations. We had a SLP assess him and they gave us some pointers (which we’re trying to do) and suggested we see a developmental ped (appointment coming up).
Have you gotten a speech therapy assessment done for you baby?