Sorry for the length, but wanted to give all of the details. Ds is 17.5 months, was a little early so corrected age is 16.5 months. He speaks very little, well below the average for 18 months which I've been told is a minimum of 20 words.
He can say mama (occasionally) and dadda, but these seem to be directed at anything and everything! Makes a noise which sounds like the name of our cat, again this isn't consistent but he's definitely does it a few times a week and says 'duff' which seems to be yes and is very consistent and his main word. He shakes his head for no, waves goodbye, points at what he wants with lots of angry 'urhhh, urhhh' noises - so there is some communication but not many if any definite words.
He understands some basic instructions eg where is your ball, clap hands, where are your feet, where are the apples, but looks at bit blank at some things I say. I find it hard to tell just how much he understands as he's such a busy and wilful little boy, he doesn't want to stop and listen or do what I ask as he seems to have a very clear idea if what he wants to be doing most of the time which he doesn't want to stop. Should probably mention that he does make eye contact, socialises well with other children and adults and will listen and concentrate when in the right mood. He also chatters quite a bit, it's just not actuall words.
Aibu to be concerned? I keep getting told that they'll all do it in their own time, he'll probably come out with full sentences, my kid was the same etc but to me this seems behind for his age and I wonder if people are trying to be kind rather than tell me straight? If there is a problem I want to do what I can to help him at home and/or get a referral, not just stick my head in the sand.