Hello Ravdeep: Well... I'm certainly no expert with regard to these topics. However, what I will say is that, to my mind, there is a difference between concentration & meditation.

Concentration involves focusing one's consciousness on a single object or activity such as a candle flame or, as you mention, one's breathing. There is a certain amount of willpower connected to this type of process.

Meditation, on the other hand, to me involves simply allowing one's thoughts to come-&-go as they will & "watching" them as they do. We may follow our breathing, or something else, during that process. And, when we notice that we've wandered off into never-never land, we return to the breath or whatever we're following. We may say to ourselves: " thinking" when we notice we've become distracted. But it is like placing a fingertip gently on a delicate flower. It is a very soft & gentle process that we repeat over-&-over. There is no willpower involved.

When difficult, or disturbing thoughts arise, we can smile to them, breathe into them, perhaps even place a hand over our hearts as a sign of our compassion for them. We can then simply allow them to fade away at their own pace. They are like little trolls come to taunt us. But they have no power over us beyond what we cede them.

So, from my perspective, if you're getting headaches, perhaps what you're practicing is more a form of concentration rather than what I, at least, would think of as meditation. That would give me a headache too!