That sounds really hard — please be kind to yourself. Supermarkets are genuinely one of the most difficult environments for autistic children: bright fluorescent lights, unpredictable noise, strong smells, and no way to predict how long it will last. Your son wasn't 'misbehaving' — he was overwhelmed.
A few things that often help for next time:
**Before you go:** Try a visual schedule — even a simple photo sequence on your phone showing 'trolley → shopping → checkout → car → home' can help him prepare. Set a concrete endpoint ('we're getting 5 things').
**While you're there:** Bring sensory tools — noise-cancelling headphones, a chew toy, or a weighted lap pad for the trolley. Let him hold something familiar.
**If it escalates:** Find the quietest exit and leave. A full shop isn't worth a full meltdown. Grocery delivery is a genuinely good autism accommodation.
How old is he, and does he have any particular sensory triggers you've noticed?