need advice about talking. I'm new here.

I'm a younger single dad (27), whose recently acquired sole custody of my
beautiful 19m.o. son. (he has been in my care for past 7 months). His
mother has essentially abandoned any attempt at contact with him or I, since
I got court order custody. What led to court: she had attempted to take
flight with him, and was providing a very squalid and unstable environment
for him, financially and emotionally - and was downright negligent. She
didn't even make an appearance for the court hearings that took place, even
though she was well-notified, (and she is actually *bitter* toward me about
the final outcome). The last time my son saw his mother was in the first
week of February.

Anyway, just thought I'd give a bit of background to my position, but the
main reason for my post is this: my son's reached a point where he can say
the words for many things, (he started talking when he was 14 mo), but he
seems stubbornly rooted in grunting and babbling at most things just
lately - it's as if he's lapsed backward. I'm just wondering how normal
this is, and what to do/expect? I find it kinda frustrating to deal with
him, when I
know that he knows the word for something (as he's said it in the past), but
refuses/forgets-how to say it. I'll make games of it, play with him,
attempting to get the proper response.. ..but he'll just kinda grunt or
babble something that doesn't sound like the word at all. I'm just a little
concerned.

The thing is, I know that he's talking at his daycare, as the workers there
tell me all about how talkative he is, how many words he seems to know..
...and I don't hear much of it.

Anyone experienced out there with anything similar? I'm wondering if he's
holding on to the helpless baby phase with me, as it gets him a certain type
of attention? I just don't get it.. ..it doesn't seem intentional at
all - he appears genuine in his confusion.

Ty