GI issues are common in ASD especially constipation. Have the doctors done any testing? Ask referral to paediatric gastroenterologist who will actually do some testing (stool test, scope/pill cam, x- ray, etc). To say they don't know without testing doesn't mean much. In the interim, try magnesium citrate to keep the bowels moving.

I wouldn't get hung up on the aspergers diagnosis. Under the new guidelines, it's all ASD now so it's not going to be relevant going forward.
Out of curiosity, what is the correlation between shots and constipation? Could it just be coincidental timing?

My son was diagnosed with Aspergers and has always had a speech delay. (I thought the same thing, but I chalked it up to I got him a diagnosis to get the services he needed so I didn't argue the point. He didn't start talking until he was 2 1/2. Also, he has always had constipation and toileting issues. He was still wearing pull-ups in the 2nd grade due to his constipation and having accidents. I don't believe it has to do with his shots, but you never know. Talk to you doctor about what you can do. My dr. has told us to use MiraLax because it wont hurt him and to watch his diet.. I'm still going through this and my son is now 12.

I was told by the developmental pediatrician who diagnosed my DD that the difference between Asperger's and High-Functioning Autism is that the diagnostic criteria for Asperger's specifically excludes having had a speech & language delay. Hence my DD's diagnosis is HFA rather than Asperger's.

I understand with aspergers they can either have speech delays or excellerated speech development in early years. As far as the constipation issue that could very well be a sensory issue. I understand from this site that constipation is a common complaint on the spectrum.