I have issues at C3-4 - for one thing, a nasty herniation and it does at tiimes make me feel "foggy" when the pain is severe. It doesn't always bother me, as I can put me soft collar on, and it will subside after awhile.
So since you have multiple issues I don't doubt that it can make you feel foggy.
Do you have a recent MRI of the cervical spine? If you do, post it here and we can help you better understand what's going on (if you NEED the help, that is)
Take care and hope to hear from you soon. Hugs, Lee