B737-800 First Officer reported a flight deck hypoxia event due to a pneumatic bleed valve issue that resulted in expeditious handling to a divert airport.

Narrative

While cruising from at FL320 we were encountering some turbulence. After inquiring with I believe ZZZ Center about ride conditions; they advised us to descent to FL280 for better ride conditions. We accepted the clearance and started our descend to FL280. I dialed in 28000 ft in the ALT MCP (Mode Control Panel) window hit ALT INTV and to expedite getting out of the turbulence faster elected to descend with V/S mode set to 1500ft per minute.Somewhere during the descent; I believe around FL290; we received a MASTER CAUTION light. First thought was OFF SCHED DESCENT; but it was actually DUAL BLEED to my surprise. Followed by the BLEED warning approximately 25 seconds thereafter.I said my aircraft; flew; and the Captain ran the QRH. We were able to fix the DUAL BLEED situation by following the QRH procedure and closing the ISOL VALVE. BLEED error could not be fixed with the trip reset button.We encountered some symptoms of hypoxia during the event; but could not confirm with pressurization gauges. It may have been due to less air coming into the cockpit as all air was almost removed from pack1 which mostly feeds into the cockpit.We elected to do a precautionary diversion as we felt safer to divert instead of taking a plane over mountainous terrain with possible pressurization problems.Cause: I don't know; but the QRH doesn't mentioning using APU air if Engine Bleed 1 is turned off with the ISOL VALVE closed. I suppose we don't use it since the bleed line could be damaged and that's why we don't apply APU air?