If your seeking a diagnosis then a psychologist will tell you that your experiencing depersonalization, if your seeking medication then a psychiatrist will tell you that your suffering from depression and give you medication. If your seeking alleviation from suffering an awakened one will tell you to know thyself.
What you can do to fix it is to gain insight into the nature of feelings, thoughts and all phenomenon. Observe all your internal phenomenon see how your thoughts, feelings, sensations arise and fall away, they come like bubbles in the sea then they pop and go back to the sea. Notice how everything that happens internally is like this, not one single bubble lingers very long and even if it lingers its not forever, its not permanent.
Next is to analyze who is experiencing these bubbles, might what you take yourself to be actually turn out to be just another bubble? Sit, relax and just be with the everpresentawareness of the moment watch all internal phenomenon as just bubbles on the sea, notice how they come linger for a bit and then go away, nothing escapes this, everything comes and goes. Now observe what doesn't come and go, even the I, or the sense of self arises in that which doesn't come and go and that which doesn't come and go can only be pointed to with words, it is timeless, attribute less, beyond time and space and is everpresent right now its all there is its the observer of all phenomenon.
So you might ask how can this help you who cares? Well once you are able to notice the impermanence of all those things going through your mind you can be less engaged with all the phenomenon, kind of a divine indifference and once you have this detachment things stop affecting you as much, and negative feelings stop having the power to control you and take over your awareness. Once this is the case and you start analyzing what doesn't come and go and you find that which is always everpresent and you start to just rest in that seeing then you find a peace beyond anything the world can offer you. Once your stabilized in that no matter what bubbles comes or goes you have nirvanic peace, timeless contentment.
This takes no belief, no action, no philosophy... nothing, just throughout your day observe the impermanence of everything... for example:
Thought, emotions, hungers, desires, clouds, rain drops, bubbles, humans, animals, plants, stars
They are all impermanent, nothing you can find in this world has any permanence.
Next find what is observing all the impermanence, find that which never comes or goes, never arises or dissipates, find that which is the observer of the body, mind, thought, emotions, desires and when you see that there is nothing other than that, stay as that, realize you are not the body or the mind. See that you are stainless, unborn, undying, forever, everything and nothing, beyond all things yet immanent in all things. Once this recognition is made, what bubble could hurt you even a bullet to the leg is happening in your awareness.
