It is difficult to comment on your particular case without knowing all of the details, but I can give you my general impression. There are three basic reasons why someone might feel worse after acupuncture (including headaches, dizziness, aggravation of symptoms, etc.). The reasons are a "healing response", overtreatment or incorrect treatment.
First, there is the idea of the "healing" response. This is an idea that practitioners subscribe to in varying degrees, but essentially it looks at some temporary side effects or aggravations of symptoms as a positive step in the rebalancing of the body. Headaches for example, are not uncommon when people are detoxing from drugs, foods or even lifestyle habits and acupuncture can quicken the detoxification of the body. This also holds true when certain areas of tension in the body are released, where people may experience some pain or tension in other areas as the body rebalances. Whether or not your subscribe to the idea of a healing reaction, the bottom line is that you have a headache, for example, after most treatments, or your symptoms are consistiently aggravated after most treatments, you are probably being overtreated and/or incorrectly treated. If it is not a consistient reaction, then you will have to trust yourself and discuss openly with your practitioner as to whether or not you feel it is an appropriate response. Many times you may have to look at changes in other signs and symptoms and balance them against any side effects you may experience from your acupuncture treatment. If the signs and symptoms are overwhelmingly improving, then I would imagine that any adverse effects of the treatments would stop after 4-6 treatments.
The second option is being overtreated. This is somewhat more common in TCM style techniques, particularly from practitioners who use strong needling and manipulative techniques than it is for "lighter" styles such as those common in Japanese acupuncture - however, it can happen in any style of acupuncture, bodywork, energywork or herbal medicine. This again, is a judgement call on your part and involves a discussion with your acupuncturist. This is why it is very important to be honest with your acupuncturist when you have follow up intakes. Even if the majority of your symptoms are improving and overall you feel better, pointing out your negative experiences is important as it helps the acupuncturist to adjust the treatment (maybe lighten the techniques, or change some of the points).
The third option, then, is an incorrect treatment. This can be just a poor choice of treatment points, or an incomplete diagnosis. This is another reason why it is important to speak with your practitioners about all of your positive and negative symptoms. With all of the feedback it is easier for the practitioner to modify the treatment or even change the initial diagnosis. An example which could lead to a headache would be misdiagnosing a condition as solely deficient when it has strong excessive components. If you were to strongly build the persons energy first without clearing excess symptomology they could experience an increase in symptoms and/or have too much energy rising up leading to symptoms such as a headache or dizziness.
Well, I hope you find this information helpful and that your condition improves. My feeling is that the headaches and other symptoms such as excessive thirst are temporary and will go away after the first few treatments, but you should trust yourself as to what is natural and discuss this openly with your practitioner. If you continue to experience the headaches or other strong symptoms consistiently even after speaking with your practitioner, you may need to consider a different style of acupuncture and/or a different practitioner.
Yin Yang House Acupuncture & Energy Healing Clinic