Re: sore throat/sore neck
I'm not trying to worry you, but you have some warning signs worth checking out.
I would get into your doctor as soon as you can. There is a very bad flu going around which starts with a terrible sore throat, and you need antibiotics started to avoid it morphing into pneumonia. (That happened to me and my husband just last month).
The white patches in your mouth/tongue sound like thrush, don't know much about that one.
The other thing that comes to mind with the stiff neck is possible meningitis. Can you touch your chin to your chest. Are you eyes very sensitive to light? I had meningitis last April, and spent 4 days in hospital for that.
Get into you doctor, and don't wait till it gets any worse. Good health to you