"I've been trying to figure out why I mostly felt hits in the head/brain/scalp"
could be because your main issue are the critters that love that part of the body, therefore there are there the most, therefore you feel them most there
for example, specifically schistosomas (or other flukes too actually, such as hepatica, opisthorchis based on my experience) make their home in the scalp and/or any "hairy" area on the body
but it's also microfilarias favourite spot and both these, flukes and microfilarias are in trillions in volume, so no wonder that you feel them most there, but this is just my best guess