Magick hurts me ?

I don't have that problem, I'm just interested.

Try eating and drinking before casting. Could be part of the problem.

As for headaches or other ailments, try opening your body in that area. I personally do the Middle Pillar and it clears up my headaches, colds, etc. by the time I finish. Maybe incorporate that into your practice at the end for a few times to see if it works.

Thats b. S. Aeson and oakgrove. Meditating helps you focus more, increasing the probability that the spell will manifest. If you do not ground and center correctly you will feel ill because the magick is using your energy and not the energy from another source channelled through you that can sustain the spell. You both are confusing the two. Look it up.

Do you cast too often and too many spells?