I am not surprised you are still experiencing neck stiffness. It takes many months of discipline and proper care to heal a concussion induced neck injury. I would not be surprised than many of your current symptoms are related to your neck as well as some brain shaking.

If your chiro was doing 'twist the head and pop the neck' adjustments, I suspect you still need more neck care, but much more gentle neck care. You also need to practice good neck posture, especially when sleeping or resting. Lifting weights can cause neck muscle tensing that can be counter to good neck healing.

What besides the eyes watering did you experience when you bumped your head ? Did you experience any strange tastes in your mouth ? Or a sensation like you bumped your nose ? or any vision changes/difficulty focusing, even if only for a few seconds ? These are all signs of a concussion.