Andrew_P
In between here and there
I'm absolutely not an expert on sports meds. but my guess is that it could be your neck/head position on the bike.
Best wishes anyway.
I was suffering really badly with headaches when I switched to a road bike, I put it down to the new bike. Ended up at a Chriopractor if you beleive the mumbo jumbo a problem my left shoulder had caused my neck muscle to shrink (tighten) and caused neckache that was reffering to my forehead.
To be fair, I could feel the main neck muscle on my left all bunched up and tense on the left right at the top and to be fair after a few visits the bike was reallly comfortable and no more head and neck aches. Was releived of quite a few quid as well but it worked for me.