Look at both pupils and see if they both react to light equally. If not go directly to the emergency room. Otherwise, doing the sort of work you describe you are probably looking down a lot and straining your neck while spreading concrete. I'm guessing you stretched something too far and got a light sprain. This can cause the pain in forehead and neck, you might also see a flash of light as it first happens. If it doesn't go away after about 24 hours you might want to consult your doctor.
thank you eyes reacting fine so will see how i feal 2moro..sleep easier cheers...
How old are you? If your older then you want to be checked for sure. Make sure your not having or have had a small stroke. Also when bending over if your head hurts can be something much more serious.