I'm 40 jus had a hysterectomy and have no energy? ?

Healing. It is common to have fatigue after surgery; a great deal of your energy is being directed towards the healing process. This usually begins to improve 2-3 weeks after major surgery. As dr. Cunnar says, anemia should be ruled out to be safe.
Anemia or normal. Depending on how long ago you had your surgery, you may just be experiencing normal post-operative recovery fatigue. If the fatigue is severe, or if you are having any pain out of the ordinary, see your physician. Sometimes, anemia can present after a major surgery like a hysterectomy. Your physician can diagnose this with an exam and a simple blood test.