Mom's with Autistic children

Or children on the spectrum, what were your first indications that something was (for lack of better words at the moment) "off" or different (and I don't mean that in a negative way at all, I'm just unsure of the words to use)
     My son is 20 months old and has feeding difficulties. I take it as very picky but he has swallowing issues and some texture issues. He only says "mom" and "dad". He has temper tantrums but I'm not sure if it's "terrible twos" related. I feel like something is off but then again I feel like he is just so active socially and his eye contact is good that it makes me feel like he is just learning differently. He is in early intervention but I want to make sure I'm taking all of the necessary steps. He has had an upper GI test done (swallowing study) and everything came back normal. 
So I'm just looking nice for some advice on how to really figure him out and lately it's been such a hassle with both him, doctors, and 3rd party people throwing unwarranted parenting advice... My nerves are shot 😕
   I also would never ever love him less or anything if there is something going on, I just want to make sure I'm on top of it to make sure he has all the help he needs early on whether it just be a delay or something more extreme. ❤️