I believe what you experienced was a rather intense bout of orthostatic hypotension.
Orthostatic hypotension is an excessive decrease in blood pressure when a person stands up, resulting in reduced blood flow to the brain and in some cases, fainting. Almost everybody has experienced this at one time or another. The symptoms of OH are feeling faint, light-headedness, dizziness, blurred vision and confusion.
Add to this that you had been feeling anxious for a couple of hours and had not eaten anything that day, it's no wonder you had a more intense reaction. This could also easily explain why you seem to have forgotten what you'd originally gotten up to do. You became so focused on these feelings, fixing the router went totally out of your mind.
Since you say you have a long list of things that you're worried about, why not see your doctor and discuss these issues? Be sure and bring up the OH.
Just to be on the safe side until you see your doctor, the next time you've been sitting or laying down for awhile, get up very slowly and then just stand there for a few seconds until your blood gets pumping again.
I'm sure this is nothing to worry about, but it's always best to let your doctor know what's going on.
Peace
Greenlydia