Hi. I agree with the posts.
Depression is the most likely cause of the lack of emotions. In fact one of the classic signs is called Anhedonia - which is an inability to feel pleasure. Of course we assume this is a new thing and not something you have always had [which could be due to other causes]. Trauma and conditions related can also lead to numbing and anger as mentioned already.
After 4 years of this, lack of concentration and memory problems can follow. It is important to get this sorted as once treated to Remission, these symptoms will improve. Having said that some medications can also make people feel a little numb.
So I agree with the posts so far. Please see your GP if you haven't already. If you have and am stuck, ask for a referral to a Psychiatrist for a thorough Assessement and a Psychologist or Counsellor to help assist you.
Meanwhile lifestyle measures are Complimentary. Exercise, giving up alcohol and cigarettes and Krill Oil can help boost your brain's recovery. Sleep is probably the most important.
It is likely that your symptoms can be helped.