You were officially in menopause when your organs were removed. The premarin likely kept symptoms at bay. But it's odd that you stopped taking it in 2015 and are just now experiencing debilitating symptoms.
I had a hysterectomy 12 years ago at age 49 and the symptoms hit hard and fast. The worst ones were depression (to the point of being suicidal), anxiety, insomnia, scary memory loss, couldn't focus or think straight, extreme irritability even over the smallest things. And those weren't the only ones. Hot flashes were only mild. I had to try various forms of estrogen before I found one that helped most of my symptoms.
Women without ovaries are at increased risk for many health problems since the ovaries produce health promoting hormones a woman's whole life, especially androgens after menopause. Estrogen has been shown to mitigate some of those risks. I don't know if I could function without it.
Best of luck in getting the help you need.
It might be hormones made in your adrenal glands. Your adrenal gland and ovaries are both responsible for hormone production, as well as other glands in your body. I have had one ovary for 10 years, and have symptoms like you describe. I'm just not the me I used to be. Doctors are not understanding. My testosterone tested low, so now I'm taking large doses of DHEA, which is an OTC precursor to testasterone and estrogen. I feel a bit better, but not much. There are also several plants and herbs that act like estrogens in your body that might make you feel better, red clover tea is my favorite and tastes great. Since you don't have ovaries, you might want to balance these things with progesterone if your doctor will prescribe it, or get a OTC progesterone cream, but I'm not sure they are the best to use.
I sympathize with you. Doctors are not understanding about hormonal issues at all, and the testing isn't accurate. Our hormones impact everything.