Welcome! I'm sorry that you feel sad about this. Is it because you don't have anyone to talk to about the milestones who can relate? It's hard when your isolated.
I recommend seeking out activities where you might find other kids like yours. For example, science museums, bookstore and library clubs, art museums, GT classes if available, lego classes. Although it's nice if our kids get along with everyone, sometimes it's nice to give opportnities where your kid will have fun, even if it means he's with older kids.
Every kid goes at his own pace, and I suggest just supporting and embracing the uniqueness of your kid. I hope you have some family support - that helps a ton if you family gets you and your kid.
Sorry, not a lot of wisdom. If there are particular areas where you and your kiddo are struggling, I think more people could advise on specifics.
