There are a lot of factors to be considered, why you had the surgery, your age, weight, general health, diet,etc....It takes some women longer to heal and recover then others. As someone else said you are also recovering from the anesthesia.
I remember when my DM had a hysterectomy. She said after 5 or 6 months she felt better then she had in years. Be sure to get enough sleep, plenty of liquids and enough high quality protein in your diet. A good multi vitamin wouldn't hurt either.
You should soon be feeling a lot better. If not, discuss it with your doctor.
Take care of yourself! :D