i've also posted millions of times on here about my DD who is now 2.6.
her speech is extremely slow, at 2.5 she had maybe 10-15 words and that's being generous. i've taken her to the doctors numerous times, had her ears tested, just about everything literally.
she was assessed at 2.5 and was found to be 6-8months ahead in everything apart from her speech - where she was classed as being where she should be....very odd considering every other child her age and below were having bloody conversations with you 
anyway, literally about 2-3 weeks ago, the words have started sprouting out, there are now too many to count!! its so true what the HV said, she will do it when she's ready.
the advice i was given, was not to speak for her, not to say "say x y z" to her, when she was asking for something to give her a choice and say the words to help her say them to. Positive reinforcement is a good way forward to, for instance if he is saying ".at" for "cat" say thats right good boy "Cat"...dont tell them the word is wrong just praise them and then say the word correctly, they'll get there eventually honestly lol
also, at this stage they are more concerned with their understanding of words rather than the spoken words. Does DS understand simple instructions like "go get your shoes" or "wash your hands now" that type of thing??
i have no idea where this influx of words come from, but they are flying out and are too many to count.
advice i would give, is you know your son better than anyone. if you feel there is a problem, do not be afraid to get it checked and push for help or assistance if you think its needed. in the meantime, talk to him all the time, read to him and play games where you need to take turns, as this helps with the forming of a conversation as in "i talk, you talk" type of thing.
x