I'm not very familiar with the anatomy of the brain Ljubica but the pain was about 3 to 4 inches behind my left eye or at least that's the way it felt . Somewhere in that region. And unfortunately I wasn't really paying attention to it but I would have to guess that it was about 3 weeks or so into the start of my DMSO treatment. Sometimes I do still get a slight headache feeling but it goes away rather quickly after I put the pipe down. I'm still kinda undecided as to whether smoking is for me or not but I do so enjoy it.
Don't take my advice, but it might be sinus infection complicated by slight dehydration. I'm type O+ and I really can't handle tobacco well, I still smoke though. There are different ways to smoke--for instance when I smoke (roll-your-owns) I smoke with a passion--I don't just take a few puffs as it burns in the ash-tray.
Smoking is a wonderful way to relax and think clearly but I don't recommend smoking all the time if you have energy problems like I do. Let it then be a personal choice as it should be. In listening to my body I should probably cut back a little. EE helps with my addictions--but not for some reason with smoking less lol.
Had Sphenoidal sinuses infections couple years ago:), bravo, actually never connect these two things together, about dehydration, I don't know, I'm really drinking lot of water, around 3 litres per day so this not suppose to be a problem.
About smoking and O+ blood type, my father was smoker and have same blood type O+ and during 2 years of smoking (organic tobacco w/o filer) he had more headaches (not migraines) and low blood pressure, so he quit with smoking and, my brother same O+ blood type, smoked for 4 years (industrial tobacco) like 4-5 cigarettes per day and had headaches and stomach problems while smoking so he quit with smoking as well, this is pretty peculiar because I actally didn't connect their reactions on cigarettes with blood type until I read your post.