All these head feelings are coming from dysautonomia, in my experience. I’m now 60, suffering from these issues since childhood, however never understood them till lately when my condition worsened after 3 years of long flights every month.
Here is the explanation, as I see it: Dysautonomia causes nerves over reaction to what we eat, so there is a pull on nerves across whole body, and depending on body constitution, pronounced in certain areas- head in my case. So these nerves pull on the brain itself as well, since a lot of these nerves connect to our brain. This is the reason behind pressure/tightness/focus issues/ ADD etc etc. My feelings get hugely stronger after I pass stools, and subside after a night sleep. I find I have to be careful in what I eat, and always relate my head symptoms to what I have eaten in last 2-3 days.
In my opinion, this brain condition keeps our minds in overdrive condition, causing constant acidity, which weakens the digestive system, and therefore our condition worsens when we lift any heavy object as it exerts pressure on our weakened digestive system and Dysautonomia moves the reaction to our head.