Advice welcome, worried mum

Hi am new to this site, which I think is great btw. I have a almost 4 year old son, he was born 4 weeks early. He has a milk intolerance and has issues with number 2s. He has speech delay, which was our first sign, he is undertaking group salt. He has just recently started to make weird noises, which worries me. The very continuing "uh" sounds and throat noises. He also shakes his head very quickly now and then. He is currently under the health visitor and is due to start school in September. I do think there maybe a learning disability or spectrum of autism, his father has dyslexia. Not sure who I can go to for advice so googled this website, which is fabulous for the fact that parents can post their worries. Am I right to worry? He was assessed by the health visitor but since the assessment he has changed, staring into space, nodding his head? Grunting? Making weird noises? Any advice would be much appreciated. It's hard being a mum full stop but these extra issues makes me worry even more.