Im trying everyday to grt up amd make a new day.. I'm busy at work and then doing exercise and going for walk .. I feel good at the time but I when ever I sit down.I feel down.why I'm not happy??

You are really working hard at being happy, but maybe how you perceive happiness is what needs to change.

I am not a doctor and it isn't good to just guess. It could be depression, it could be a million things. My first step to ANYONE is ask them if they have been to a doctor in a while for the very basic check up. Have you had any blood work? Being tired can be the symptom of about a thousand diseases. I like starting there because you rule out the basics you may be missing. After that it gets harder. Have you ever kept a journal? Writing some ideas and thoughts down when you get these low periods may help you see a pattern. I find I am more apt to be truthful when I write. It is harder to say the hard things. Write it down feels good. Without knowing all about your life it is very very hard. But it meant enough to come here and ask. Clearly it matters to you. Please keep looking. There are ton of people who feel lonely and might be out there waiting to meet someone. Adding new and interesting people and activities often will inject some spark to your life. GOOD LUCK!