What does the fact that Gregor seems to ignore his physical symptoms in lieu of harping on his psychological hardships say about Gregor as a character?

This tells us that Gregor has a lot of emotional turmoil to deal with. On one level, his physical transformation may merely be a metaphor for the emotional transformation he is going through. Gregor must reconcile his own feelings of insignificance and abandonment with whatever is happening to him physically.