My goodness. This sounds awful. Yes. It could be a medical condition. It could even be a problem with your thyroid. Sometimes the tests for thyroid problems produce false negatives. I hope you saw an endocrinologist, not just your primary care physician, to have this checked out. If a more sophisticated test still comes back negative for thyroid, there are a number of other physical conditions that can produce the symptoms you describe. Among the possibilities are anemia, vitamin deficiency, eletrolyte imbalance, urinary tract infections, chronic fatique syndrome, Lyme disease, and even a brain tumor. This list isn’t intended to be inclusive or to scare you but merely to point out that there are many medical conditions that can look like depression. The first step, then, is to get a complete medical workup.
If you find you are medically fine, then please get yourself to a psychiatrist or psychologist for an evaluation. The symptoms you describe are also consistent with a diagnosis of depression. Depression often makes people withdraw from the people and activities they love. Fortunately, it can be treated. A combination of medicine and talk therapy can get you back to your usual self.
Please don’t wait to make these appointments. You’ve been feeling miserable for far too long. You, and your family, deserve to have a happier life.
I wish you well.