My son was diagnosed at a similar age to yours is. He had a lot of speech, but it was all echolalia, he had great eye contact and was very affectionate.
Autism is a spectrum disorder and everyone on it is very different.
I actually brought up concerns around 18 months and had them dismissed. The a health visitor brought up concerns at his two year check, by this point I was pretty much in denial. He could do things and other things he would do in his own time, that was my thinking.
He went to an assessment centre for a week and was reviewed by various professionals and was diagnosed with ASD. Once in a room with other children, it was really obvious my little boy was different to others. Now I see it as a huge blessing that he got diagnosed so early, he had early intervention and started at a special needs nursery straight away. So many people really have to fight to get a diagnosis, I was lucky.
Let them do the assessment, if he has asd you’ll be lucky you found out early. If he doesn’t have asd then you know the other way. I know it’s scary and probably feels like all your hopes and dreams for your son are being dashed but he’s still your little boy, you will still love him, and you will learn to adjust. Just be kind to yourself.