I would like to learn why I feel so exhausted after meditation as well as why in the area of my third eyes I feel strong pressure/ headaches.
When you meditate, it is very important to relax first and to make an effort without tension.
I don’t know what kind of meditation technique you practice but, in general, when you meditate you want to make sure that you are relaxed and that your efforts in the practice of meditation are done with energy and relaxation, trusting that the divine power will bless you as you relax fully.
The feeling of pressure at the third eye is a good sign that you have directed and offered the energy up to the third eye, the center of higher consciousness.
The headache is a sign that there is strain in your effort and that your gaze is focused on the physical location of the third eye, rather than gazing out and up slightly above the horizon. Avoid gazing with any strain.
Behind closed eyelids gaze slightly upward without strain, as if looking toward a distant mountain peak, which is to say looking slightly above the horizon level.
To allow God’s grace to guide your practice and bless you, you need to surrender, to open yourself and allow the blessings to flow through you, being purified by God’s power and grace.
Remember that it is God’s power that will change you, not your power, and all you need to do is to cooperate with this divine power by opening yourself and offering yourself.
Tension and strained efforts will obstruct God’s power to uplift your consciousness.
I hope that you will be able to meditate deeply, and feel rejuvenated afterwards.