18 month old referred to neurology and genetic testing anyone else been in this position?

My 18 month old son has been showing signs of autism since he was a baby, He was born through a traumatic birth and had a head lag, he isn't following any of his milestones, he is defiantly weak on the left side, I have been complaining to health visitors and anyone who will listen doctors physio etc because he seems in pain and tired a lot of the time. He is also very heavy to carry and can't sit unaided for long periods of time. He also hand flaps and his muscles either tense or he is floppy. He had genetic testing and muscular dystrophy test done last week and we have been referred to neurology. He is also hypermobile and gets into crazy positions. Has anyone been in this position?  His 4 year old brother was diagnosed with autism in February this year and I think some professionals may be putting his problems down to autism.