Greetings, Omaradib!
All of the symptoms you mention are characteristic of depression. You mention "three weeks," buy have you felt this way longer?
My own depression has lasted for years, and I've not yet been able to overcome it. But not all people who suffer from depression are so "depressed" all the time. Therapy, techniques, possibly medications may help you be productive despite the depression and may even overcome it. I wish that for you.
If you are just learning about depression, PsychCentral has an excellent
Depression Section with links to many articles and other resources. Of course, you can pick up a lot of good ideas just reading around the forums, too.
Respectful Regards to you!
__________________
My dog

mastered the "fetch" command. He would communicate he wanted something, and I would fetch it.