@Shaz51 I hope the appointment went well and that your husband is feeling better now. Insomnia and stomach problems are both common parts of people's autism fruit salads (see link below), but a GP is likely to treat them as separate issues. And they both get treated in a similar way as they would with a non-autistic person (blood test, stool sample test, ultrasound, increasing physical activity and bedtime routine).
If you or your husband want to think outside the box on these symptoms and do your own research, this resource can be a good starting point. Look under physical health and sleep disorders. A lot of the links are no longer active, but you can google the terms yourself for more updated information.
Polly's pages (aka 'Donna Williams') » Blog Archive » What is Autism? by Donna Williams