I'm struggling

Hi everyone, I don't know if I'm being an absolute idiot by being upset but I just feel like I'm failing as a mum. My little one isn't hitting any milestones at all, to the point he's not clapping, waving, hasn't said any words and won't even answer to their name. When I pick them up from nusery they don't even look at me when they hear my voice and doesn't smile at me either. I feel like I'm letting them down and I'm finding it so hard.