am i going crazy or is it mums instinct

Hi all i have an 11yr old who is aspergers he wasnt diagnoised until he was 7 although i had been trying since he was 2 to get someone to listen to me. CAMHS only got involved and asessed my son as he was on the verge of being kicked out of school because of his sever meltdowns (which havent got any better) I have a 7yr old daughter with a sever heart problem and i also have a 3yr old boy who has verbal dyspraxia but im concerned as he is showing signs of being on the spectrum but ive seen two child development doctors and i have been told basically just because i have one child on the spectrum doesnt mean im going to have another child. I just cant shake this emotion that my 3 yr old is on the spectrum, his speech is very delayed he can barely say 50 words but he constantly thinks hes a dinosaur he walks around like a dinosaur he eats his food like a dinosaur we have to call him Bentley the dinosaur or he will not respond. He is only intrested in dinosaurs nothing else. He lines them all up if i move one he has a meltdown and gets very very angry. He will not go to bed without an ipad to watch dinosaurs on. He hates going out he will walk 30 meters max then refuse to move he hates the pushchair he just wants to be carried everywhere. He has major anxiety with going to the toilet he will only go to the toilet at home or his grandparents, he will hold his bowel movement until he gets home and then will only do it in his pants. We were on holiday a few weeks ago and he didnt have a bowel movement all week he held it until we got home. He screams at nursery if they offer him a toilet break. He has never interacted with children well he lashes out alot but i know thats probably down to him being frustrated that he cant talk. Hes very aggressive to his older sister but shows no remorse for his actions. I was told that they will not look at autism until he has a full range of vocabulary but i said that could take years as he has verbal dyspraxia and they just shrugged their shoulders, my oldest son went through hell i just dont want my youngest son to should i ask for a 3rd opinion of just leave it even though alarm bells are ringing, sorry for the long post x