Anyone feel Diazepam wears off too fast?

I take 5mgs Diazepams x3 daily for GAD but it wears off very fast like 2-4 hours, is this normal?

I feel I need a longer acting benzo ie duration of effects. 5mgs feels weak if I am honest, it's really not helping much with my bad anxiety and skin burning feelings.

I feel my doctor won't increase my dose any further ( UK NHS ), honestly feel she just discontinue Diazepam in general if I say they are not effective, really can't win.

I asked 2 times for Clonazepam and was advised it's not prescribed for GAD.