migraine doing inverted postures

Whenever I do any inverted postures (especially the Headstand) I usually get a migraine, is there a way in which I can overcome this?

Usually inversions would be a good thing to do for headaches and migraines. But it sounds like the increase in blood pressure is triggering them for you.
I would avoid all inversions where the legs are over the head (head stand, shoulder stand, hand stand) and would experiment with plow, yoga mudra, standing angle, standing forward fold, downward dog and other semi-inversions.
The other possibility is to only go into the full inversions for very short periods of time on a daily basis, and very very gradually lengthen the amount of time you hold the posture.

Ahimsa, the yogic practice of non violence must be adhered to when engaging in the practice of hatha yoga. Respect your body's limitations and inner wisdom, if something feels wrong or dangerous, please do not do it.

Please consult your health care practitioner before starting a yoga, pranayama or other exercise program.