Constant Agitation - Depressive thoughts

I am a 36 year old male, self employed and single. So this started primarily after the passing away of my father in 2014. My father passed away after a prolonged battle with bacterial meningitis and I was beside him at every step. Over the last few months or maybe a year, I stay extremely agitated all the time and feel disconnected from everything. I don't like to talk much and stay away from any social gathering even if that involves my closest friends. Every single thing irritates me, whether that's a knock on the door or the constant chirping of birds outside early in the morning. I have also been having extreme difficult falling and staying asleep. On a good day, the most sleep I get is around 4-5 hrs. I sometimes become anxious over nothing and that affects my sleep and overall sanity. I just need to start feeling happy again. I have lots to be thankful for but I have just stopped living. I don't smile and have started despising my life completely.