How can anxiety make you feel faint/lightheaded even if you're not panicky or breathing wrong? all other tests come back normal.

Breathing: Is complicated sometimes... It is possible to hyperventilate without realizing it. Just taking a few deep breaths a minute is enough to hyperventilate. The classic rapid huffing and puffing hyperventilation is rare. Try breathing "from your diaphragm" when you're feeling anxious or light-headed, or grab a paper bag and breathe into that for five minutes. The dizziness is often improved.