There are several things that can go wonky and cause menstrual headaches:

The water retention can localize to a part of the neck/skull, causing pressure and ache.

There's more estrogen released into our system as our uterus flushes/cleanses, putting stress on the liver and causing numerous hormone-based reactions throughout our body.

If your uterus is storing toxins, some of these get released and cause toxic headaches. Best thing for this are colonics/enemas and making a paste out of powdered ginger and applying to forehead and taking a detox bath.

Cluster headaches (vein constriction) are more common as the body tries to bleed without bleeding to death.

Constant use of ibuprofen and other pain pills cause stress to the liver. Tylenol especially will cause cirrhosis, as bad as being an alcoholic. These pills are also very hard on the kidneys and one of the major reasons for kidney failure.

SO... drink lots of water, take walks, get a massage, avoid bad/imbalancing foods, and do the usual things to aid the paths of elimination instead.

Keep up with your liver management and this symptom should resolve itself. :) The liver manages taking estrogen out of the body. A weak liver allows it to get overdosed. I don't have any PMS since doing liver flushes. :)