Son really struggling in social situations

Hi all,

My 7 year old son has recently been diagnosed with ASD. He really struggles in social situations like birthday parties, he doesn't join in and won't go off and play unless I'm constantly by his side. If I go to sit down to talk to other parents he follows me and this can also lead to him having a meltdown but he's quite happily playing if I'm close to him. He's the same at any social setting ie playdates with other children. He doesn't feel comfortable going off with other children unless he has either me or a trusted adult by his side too. I feel like all the other parents are sitting down chatting to each other while I'm sticking with him to avoid a meltdown. It can become very lonely. He struggles with anxiety too.

I was wondering if anyone else had been in a similar situation and can offer any advice?