Lots of water, light yoga stretching, with light exercise helped me. Fatigue is common with these drugs. I'm on them too
Unfortunately Myeloma cancer causes tiredness even without the meds. Hang in there.
On the days Ron takes dex he takes it late afternoon, then takes melatonin before bed. The first time he took the dex he took it midmorning as directed and was wide awake at 2 am. Moving it to afternoon and adding melatonin made a big difference.
I'm also on velcade and dexamethasone. The dex hops me up. Not much sleep. Everybody's different it seems.