Feeling lost. Peace in being alone.

I really feel like I am fighting with something that isn't clear to me and I do not know what it is. I am unable to be happy even if I want to. I have gone through many good quotes and inspirational videos. I feel motivated for sometime and then dont know why I become motivation less again. Its just a quick change I can say. I know that this is not me. When I know that this is not me and why I am not happy or want to be happy. I am.seperating myself from everyone and everything even my interests also. They mattered to me alot but not now. I dont know why. I am unable to concentrate on one thing. I cry alot for this reason. I am trying hard my level best to focus on my career but dont know what is stopping me. Meditation too dont work. I dont know how my mood will be next moment sometimes. This hurts people and I hate that part of me. I dont want to hurt other people and I want to be alone and seperated from all all the timee. Dont know why I am finding peace in being alone.