I get headache when I attend any meeting or if I am in a group of people are talking about the matters which I have interest in.?

Emotions and Pain. My area of interest is in the way our emotions, our feelings will manifest themselves as physical pain. A common way this happens is tms - tension myositis syndrome. Pain is real in patients with tms, but the cascade of pain begins from an emotion - not an injury. A nice place to start to learn about this is the tms wiki. I also talk about it on my own website (www.Thehealthymind.Com).
Triggers. Headache can be caused by triggers and triggers can be anything. It seems like that being in a group might be your trigger. Stress, social anxiety are common triggers; pay attention to your stress level, stay well hydrated, and avoid headache toxins (caffeine, nsaids, acetaminophen, opiates).
Headches. Headaches in this setting might be stress or anxiety related. But other causes might require investigation.