What to do if I have headaches after spinal surgery, doctors keep dismissing it?

Be persistent. Be persistent in letting then know that you are having problems, particularly if your headaches are severe. If you don't get the response you need, don't hesitate getting a second opinion. While many peri operative headaches will resolve, a small percentage are causes by serious postoperative complications such as a spinal fluid leak. Hopefully you will do well.
Headaches. If the headaches are better when you lie down and worse when you sit or stand up then you may have a cerebrospinal fluid leak. Headaches can occur from an infection and irritation of the meninges around the spinal sac. Repeat imaging and blood work are necessary if the headaches worsen or if fever, chills, light sensitivity, and neck stiffness develop.