i was having headaches early on in pregnancy, i thought it was due to a stroke i had last year but doctors said not, im 29 weeks now and i not had headaches for about a month but up until then i had them daily. My blood pressure was fine so what the doc suggested was that i cut out all the foods that caused headaches ( there are actually a lot but if u look on net u should find a list of them) i did this and the headaches stopped i then reintroduced things one by one which took me a few weeks to do as my list was really long but it was worth it because in the end i was left with a short list of things i couldnt eat which were Coffee/Tea/Full fat milk and fizzy drinks. And like i said i not had a headache for a while now and i was getting really bad ones.heres a link but have a good look on a few sites as there are a lot of foods you wouldnt even think of,
http://www.webmd.com/migraines-headaches/guide /triggers-specific-foods
oh and avoid going to the chinese as there is something they put in food which causes headaches. good luck