Smoking won't necessarily help, Leaf, and it might make the headaches worse.

Sexual stimulation causes pressure on the back of the head, usually from the straining and muscle tension that occurs. If, as you've stated on that other thread, you were thought to have a potential neural tube defect when you were in utero, you may indeed have some squeezing or malformation in the back of your head that causes that pressure to be worse (something milder than spina bifida but which can contribute to headaches). I also know from your profile pic and another of your posts in which you said you were considering obesity surgery that you're overweight, and that puts pressure on the back of the head, too, and can sometimes worsen headaches. That's sometimes referred to as "pseudotumor cerebri," which is basically a pressure-related, back-of-head headache that sometimes has other symptoms, too. It's fairly common in significantly overweight people, and sexual activity is one of the things that can aggravate the headache pain.