As Sally suggests, it's not necessarily from the hysterectomy if you didn't begin to have these swings right away after the operation. But it's easy enough to check, if your doctor will do a complete workup. I wouldn't leap to antidepressants as an antidote to the lack of hormones, in any case. If your doc tests you for things like thyroid and even hypoglycemia, and if you are already cutting sugars and exercising, you might ask also for hormone tests, and see if the doc will prescribe hormones for a while to see if this eases. Depending on why you got the hysterectomy, he or she might do so if you explain the problems you are having.
Have you had your thyroid checked? This may be a partial cause of mood swings. Try lower carb diet / cutting sugars and exercise to help naturally with mood swings. Sorry you are feeling bad.