As far as pain killing is concerned, to overcome chronic shooting pains in head, I opine you to start Ayurveda medicines which are known to cure such types of headaches but equally known for slow but safe actions. Shirshoola, ardhavbhedak, sooryavart are a few categories of shooting headaches described in Ayurveda. There are long term remedies too. It is worthwhile to start since I feel you must have done all the necessary tests for excluding any lesions, compression due to cysts etc. If you can find any Ayurveda doctor near you, its good or try to consult on net with your reports. To start with Shirshooladi vajra ras , prawal pishti, godanti bhasm, sitopaladi mixed together and licked with honey ( if no diabetes) or water over few weeks and Pathyadi Kvath decoction and instilling Shadbindu oil in nasal cavities will bring some response. The degree of response will determine future course of action. Remember it is SLOW but non synthetic, safe, side effect less and economic. Easy to take. There are allopathic alternatives available in the market but not without side effects. Moreover those wont give permanent relief. Ayurveda may bring permanent relief. However, during severe pains analgesics may be taken. Herbals will not counteract with that. Give a try and be happy. Hope it helps you.