Well - I've had a lot to say on this sort of topic recently. I'll consolidate it to this: We started down the assessment path when a well-meaning preschool teacher insisted DS (now 7) was Asperger's. We did ASD, SPD, ADHD, and anxiety assessments and others. My two cents is this: if you take a PG kid to a specialist in any of these areas, they will probably say, "Well - it's not a clear cut case, but there are several indications that he could be [X diagnosis]."
This is not because the assessor is bad or ineffective. It's because a PG kid has brain-wiring manifestations that present LIKE symptoms of all those other things. They may ALSO have those other things, but it's hard to tell when the PG kid is in the throes of asynchronous development.
And I don't use the word "throes" lightly. Early childhood is really, really tough for a PG kid and the kid's parents. You don't know (can't know) what is really going on but your kid feels broken and you feel an overwhelming need to help.
I have heard over and over from other HG/PG parents that (1) it becomes clearer as they grow, and (2) it becomes easier and the kids will be more functional and stable, emotionally and socially, as they grow.
I will tell you that this has been the case for my DS. If you read my other posts, you'll see that we are hardly out of the woods. My heart still seizes when I see the school caller ID on my phone! But - things are getting better and better. His "issues" are indeed both diminishing AND coming into clearer focus now, and it's easier for us to know how to support him.
You are smack in the middle of the time that was very hardest for us. When DS was between 4-6, he just had a very tough time. And so did his Dad and I. We survived by remembering that the problem is not always that "he won't." In fact, it's almost always that "he can't." Once you convince yourself to at least consider that point - it will help guide you to the best supports. And always know that he really is trying so hard to be good. So give him lots of unconditional love. Especially when he is having a bad day.
Lots of hugs to you,
Sue
