Poll: How many words does/did you 18mo have?

CheezeFace

DS is coming up on the 18 month mark and I've noticed some language differences with him and others around his age...some a bit older, some younger. It seems as if his language skills aren't progressing at all. In fact, we had a playdate today with a friend the exact same age - we haven't seen him in a month - he wasn't speaking before but today he pointed at the pool and said, "Go swim". 

He really doesn't say any words other than "no!" and he's mastered that one.  He's said "mamamamama" and "dadadadada" forever but, really, not another word. If I ask him what sound a car, cow, puppy, cat, etc...make he'll mimic the sounds but he won't say, "cat" or "dog".

He understands quite a bit: "go upstairs".  "Let's take a bath!" "Find your shoes." He follows through with the appropriate actions.

There are some language issues on my H's side - his parents as well as my H tend to struggle with reading/grammar and I recently found out that H was in resource classes when he was in primary school (behind in reading as well as comprehension and I would guess speech issues). 

I don't like comparing my kid to another kid but I can't help but be mindful of this potential issue.  Oh... And then I, stupidly, Googled what an 18 month old 'should' be saying.  Then I came here to talk to real moms

So, does this sound like something I should wait out for a bit more before I become concerned? Should I be more proactive considering H's history? Should I be working with him in some way other than just talking and naming things?  Did your LO's have a major leap and just wake up one morning and start communicating?

TIA