OP - clearly not a parenting highlight, but we ALL react badly at some stage. It IS frustrating when they don’t seem to ‘care’ about something whether it’s a wet bed, lost items or whatever.
As most people have said...
GP - for UTI, diabetes, etc. Worm meds.
School - for any issues, bullying, increased workload, new child, disruptive child, change in routine.
Fluids - more to drink during the day. Personally I don’t agree with limiting fluids, not even before bed. Bladders need to be encouraged to work properly, not ‘managed’.
Lifting - I don’t agree with either for the same reason. The only time I’d do this is on holiday if the bathroom isn’t easily accessible.
I’d rather fix the actual problem, than simply avoid a wet bed.
Deep sleep - accept the reason might just be this, due to school, growing (internal changes before a ‘growth spurt’, hormonal changes (hormones control your ABILITY to wake for a wee) etc).
Double sheet/waterproof layer the bed. Reassure DS that it’s just something that’s happening for now and you both need need to find out why. Explain why it’s important he talk to you about anything he’s ‘thinking’ about - even if it’s not directly affecting him (sometimes they worry a LOT about friends at school whether that’s stuff at school or something a friend has told them about outside of school)
If you’re on half term now, try to spend time together, keep it low key and do as has been suggested and hopefully it’ll sort itself out. Keep the bed double sheeted, it’s surprising how often it’s a complete bonus in the middle of the night and it does no harm.