Hello, Ephemerid.

You were saying that initially this reaction was pronounced only after a long and intense practice session. Now, after having practiced regularly for weeks or months, the sensation comes up quickly and more pronounced. Do I understand that correctly, yes?

Usually practice itself causes two things to change: The amount of energy you're being able to move around and your ability to feel energy moving.

More energy circulating through your system while practicing will have bigger effect on blocks. Imagine a pipe that is partially blocked. Now imagine moving more water through the pipe. What you get is higher pressure. Energy blocks cause unpleasant sensations, energy circulating without much blockage cause comparatively little sensation. So your sensations seem to indicate that you have energy blocks in the respective areas, and when your practice stimulates energy circulation you notice the blockages more strongly because a higher energetic pressure builds in these areas.

On the other hand, also with continued practice, the ability to feel energetic sensations is also improved. More energy flow and this enhanced sensitivity lead to noticing energetic blocks more strongly.

While unpleasant sensations during energy work may happen while energetic blocks are wore down, you should be careful and gentle when you encounter pain or other alarming symptoms. In this case try to practice less intensely in a session and have more sessions instead. This applies to energy work in general.

Energy blocks in the head - third eye, nasal-eye bridge, the facial area, may be due to factors like trying too hard to concentrate, putting too much time into mental endeavours without counter-balancing them, etc. Wherever your attention goes, your energy goes. Staring at a screen for too long, or being "too much in one's head" very often, many of these activities create tension in the head, for example also by making the neck tense and blocking smooth energy circulation. Also anxious worry might cause one to be locked into one's own thoughts, and hence the head.

Counterbalancing such behaviors with other activities, gentle energy work, sports, all grounding activities, plus checking out all the things Beek mentioned might all help.

What type of meditation are you doing? It might be helpful to switch meditation object as well. For example watching the breath at the nostrils worked really badly for me because I had blocks in the nasal, eye and forehead areas.