Sounds like post concussion syndrome...lots of rest is the first thing prescribed.

I wouldn't worry that you have any kind of disease. If you had a problem with your kidneys you would know about it because you'd be in unbearable pain in your back and abdomen. And I'm pretty sure there'd be huge warning signs with liver disease,too. Right before my MRI I started to have panic attacks about whether it could be a brain tumour because my headaches often feel like something is pushing against my skull and I thought maybe my accident was a 'sign' to get checked etc... There was no tumour, of course

Other people will have better advice that me, but I just wanted to help ease concerns about very unlikely diseases!