Help- keep monitoring/GP/Emergency??

I took DS to the dr's a couple of weeks ago as he has been making an audible rasping wheeze in with each 'in' breathe regularly throughout the day. The GP put it down to a behavioural thing, experimenting with sounds and showed me how to check around his ribs and chest to make sure he is not having problems with his breathing. He also mentioned to look at his throat and see if its drawing in. He checked him all over and couldn't see anything wrong so i relaxed and haven't really worried too much when he has been doing it.

I had him lying down across my lap today when he started, he tipped his head right back and i got a really good look at the base of his neck for the first time, and it is really drawing right in with each sound he is making.

So now i am freaking out! Any ideas on what i should do? In between them he seems absolutely fine, maybe grunting a bit like he is trying to do a poo? He has done it twice in the 40 mins since he last woke up, then did a big burp and hasn't done anymore.

If you're really worried do you have another GP you can see to get a second opinion?