How Long Should Premarin Estrogen Hormone Be Continued After Subtotal Hysterectomy?

Hi,

I had subtotal hystrectomy with removal of the right ovqry amor than one year ago. I am on premarine osrogene hormone, I feel lazy, fatigue, depressed and gaining weight.

For how long shall I be on this Premarine? and what will happen if I stopped it suddenly/

Thanks

Hoda