You need to do something that provides a creative/ambition fulfilment. Get a hobby that gives you something at the end (writing, painting, model building), get a girl, aim to get a better job, take a course, play a sport, something like that. You can't live life without having something to strive for
Pretty good advice.
Despite having a live-in girlfriend I've actually been feeling pretty similar (obviously not with her), so I'm started climbing again and going to the gym all the time.
Surprising how just a few activities a week and interacting with other people helps.
Make an effort to get in touch with people/meet new friends :)
Losing my dad yesterday made me feel dead inside, and I think everyone here knows how mentally disturbed I am... which helps it none. Right now, I'm not even on the freaking planet. I'm exactly where you are at, but perhaps in a worse spot then you are.
People here suggest some good things for you to do like get out more, meet people, and perhaps get a friend or two. Listen to those who are serious.
This might sound strange, but see a medical professional. I am not talking about getting some mood drugs to make you feel better, buy you may be low in testosterone. What you say about feeling really neutral not happy or sad sounds like what a friend of mine went through when he found out that he was running on extremely low testosterone. You may be in a very different situation, but a doctor would know best how to help you.