There are a few thoughts I have for you, one is its very normal to feel depressed its from a few reasons one you just had a very serious operation, you where thrown into a instant medically induced menopause not gradually into as nature intends.
My advice ask Dr about bio-identical hormone replacement it helps with most symptoms you may have to try two or three times before getting the right combo for your anatomy every one is different.
Ask Dr first before using any herbals,,there is a procuct called Black kosch sold over the counter it helps many, may or may not work for you, with drs permission worht a shot,
I dont ever advise premarine, its old school, bio is the way to go, also short term anti depressant or anti anxiety may ( would) help you,,,there is no shame in that your bodys been through a trauma,
try to be around people do things that are fun for you, talk to your friends and family about how your feeling that helps too,.
Please see you gyn actually Id try a new one if I was you a second opinion doesnt hurt and I hardly ever hear of docs prescribibg premarine anymore, also see your family dr about the depression.
C
I had one in 2007 at the age of 33. Because of a seizure disorder, I couldn't do HRT. I used a soy menopause pill from Vitamin World. I still had hot flashes but I definitely noticed that things were worse when I didn't take it so I know it was helping. I took it for about 2 to 2 1/2 years and then went off of it and found I did okay without it. You might want to check and see if something like that helps.