Adhd vs autism

Those of you with ADHD kids..

When they were toddlers, were they behind with certain milestones? Did professionals question autism, too?

My kid does not fit into a box. He shows characteristics of both, but he's missing the big red flag signs of autism. I've read there's a lot of overlay between the two. He definitely shows signs of ADHD, but there's a lot he doesn't understand and I just feel like it's too much to "just" be ADHD.

I'm getting him all the resources I can...EI, speech, OT, developmental pediatric referral. I just have so many emotions on a diagnosis and I question everything.

Eta: he's 2.5