We knew my son had quirks but didn't think much about them until he didn't talk. My mother in law mentioned she was very concerned so I researched like crazy and found he had several red flags. He was diagnosed this year with classic autism. The thing about autism that is confusing though is the spectrum and how no two children on it are the same. My son hugs and cuddles, and has always laughed or smiled. However he didn't use eye contact, lined up his toys instead of playing with them, used patterns for everthing including himself, had severe meltdowns where he cried, screamed, and thrashed around for several hours at a time. We couldn't take him to the store, restaurant, anywhere in public or it was too overwhelming for him and he would meltdown. He wouldn't respond to his name and basically ignored us when we approached him. He really went to his own little world when a stranger approached him.
I'm so thankful for my MIL for even suggesting it because after First Steps, and now special ed preschool he is doing amazing with learning animals(that is his passion), and sign language so we've broken the language barrier which results in less meltdowns. He now plays with most of his toys appropriately and responds to his name half the time. We still have a long way to go and a rough path to walk but it will be ok:)