I am experiencing the same thing right now. I never thought (or was told) to have my neck checked. My doctor(s) think I have torn ligaments in the back of my neck and C1 & C2 vertebra are horribly out line. Fourteen months into all this and the doctors still don't know what is causing the headaches. Please be careful will adjustments....you are so close to your spinal cord up there. I wouldn't want the chiro to cause you anymore problems.
ps I can't believe your gp laughed. Nothing to laugh about!