As someone that has worked for a Chiropractor, and had clients that has seen a few - I am sad to say I do have a slightly jaded opinion of them... Especially when they feel they can 'cure' the body.
I also suffer headaches and migraines, which I know from first-hand experience - It is not fun.
However, I can speak from my experience what I know works for me. Reflexology, Massage and MSM (a natural supplement that you can find in the health food store, and it does not cause a yeast infection in the body - at least, not for me.). Oh - and I do take a probiotic as well. I prefer refrigerated probiotics as these are more potent and work best.
I noticed as I had weekly sessions in reflexology (as I was in school - we worked on each other - so it was the perfect way to gauge this), my migraines/ headache pain lessened DRAMATICALLY, along with the frequency. I have a few triggers - and they lessened as well. Massage helped me, too - but not nearly as much as the Reflexology did. I also have a few oils (one from Hawaii) that works on the neurological issues many can have - and it's amazing! :)
As for yeast - this can indicate infections in the body as well. Yeast typically gathers in the colon first. A colonic may help (Colonics are a very good way to avoid a cold if you get one in time - usually just as you feel the cold coming on) Or you could just decide to stop taking these supplements.
If you are really interested in helping your body and getting yourself healthy, the best way is to watch what you eat as that can help your body. Eat raw veggies, raw fruit, nothing processed or greasy. Lots of water (people get headaches if they are dehydrated), less sugar. You eat the way nature intends for you to do so. (There are no 'supplement' trees out there in the forest, right?)
If your headaches are related to hormones, then reflexology and/ or massage can assist you a great deal naturally as well, just as it can if it is stress related. I know I prefer having an hour massage over a 15 minute adjustment any day!
(Remember - Migraines are usually linked to digestive issues, feminine issues or stress. Mine are triggered by sinuses and stress. Reflexology works great for this as it works for both.)
I worked for a chiropractor in Sterling Heights that actually used scare tactics to gain clients. He had the same clients in four times a week, weekly for longer than was necessary for their complaints. The body cannot handle adjustments that often as that can cause damage to the ligaments and weaken them. Many are out to use up the insurance money clients have. It is very hard to find a good Chiro that does not embrace what natural healing should be about. The person I was with decided to touch my son when I had him with me one day when I was just cleaning my massage studio without my permission - he was messing with his neck. I'm lucky I got my son away as quickly as I did, as I have known others that have had seizures from just that. And this guy did not have my son's medical information~ just a 'God' complex.