I think a little of both.
Hello,
Weight gain is a common side effect which is experienced by women after hysterectomy. Start brisk walks daily in early morning and take less of fried and junk foods. In my opinion you should consult a gynecologist and start with hormone replacemenr therapy.You can also take Selective Estrogen Receptor Modulators like Femarelle which derived from a botanical source (Phytoserms) or phytoestrogens which have an estrogenic effect on the body and therefore create a moderated estrogenic effect.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.