Do I need to see a doctor again or shall I just go to hospital? (Concussion)?

The symptoms you describe can be down to a bad concussion, however the fact that they are still troubling you nearly three weeks after the initial injury lead me to conclude that some inter cranial bleeding/bruising may be present. That is when your brain has been shaken around inside your skull. To be completely honest it doesn't sound like your doctor is taking your symptoms very seriously in which case i would go back to the hospital and tell them that the symptoms are getting worse and you would like further tests done. This may mean an ex-ray to rule out broken/damaged cervical vertebrae (first 7 vertebrae from the head down), or a CT scan (a scan of the scull and cervical vertebrae) to rule out any bleeding/bruising within the brain, or damage to the vertebrae and/or in-vertebral discs (the cartilage discs between each vertebrae). To find more information on the vertebral column go to the following website a href="http://en.wikipedia.org/wiki/Vertebral_column" rel="nofollow"http://en.wikipedia.org/wiki/Vertebral_c…/a or a href="http://www.nhs.uk/conditions/ct-scan/Pages/Introduction.aspx" rel="nofollow"http://www.nhs.uk/conditions/ct-scan/Pag…/a to find more information on having a CT scan. I hope this has been of help and good luck.