Pilot reported experiencing debilitating symptoms due to carbon monoxide poisoning in flight. Pilot temporarily lost then regained consciousness and landed the aircraft.

Narrative

I departed for my sixth jumper load of the day after flying for 2.5 hours. During that day; I was refueling the aircraft every 1.2 hours or every other jumper load which made this load the one right before I fueled again. My first indication of impairment was a feeling of shortness of breath at approximately 8000 feet MSL. I dismissed this feeling as I have been getting over an illness and it was similar to the feeling I had flying Cessna Caravan at 14;500 feet MSL for the same operation just the week prior.At 9;500 feet MSL; I was about to make my two minute prior to 'Jumpers Away' call when I started feeling clammy; nauseous; and was rapidly losing my vision. Upon this feeling I immediately called for a bailout to the four fun jumpers in the back. My last memory before falling unconscious was the door opening and myself making a radio call to ZZZ Approach about the situation. I do not remember the jumpers leaving the aircraft or how they did it as I entered a dive. I started to regain partial consciousness at around 8000 feet MSL. Using sources which all indicated an initial -2600 feet per minute dive; I was unconscious for around 35 seconds. I most likely hit my jaw on the yoke as I felt a soreness later on. After regaining partial consciousness I was unable to see where I was. My vision was incredibly tunneled with a yellow tinted central vision. I can only remember glimpses of the descent using my altimeter for ground clearance and my iPad for heading and direction as they were immediately in front of me and the only things I could see. I have no recollection of the landing especially in regard to where I touched down. The dropzone is positioned at the approach end of Runway XX which has zero view of Runway XY which I landed on. After veering off the runway and at a complete stop; I was able to figure out where I was. I pulled the mixture and then crawled through the open jumper/cargo door on the airplane. Due to the vagueness of the emergency; the jumpers on the ground were under the impression one of the departed jumpers was having a medical emergency. A few minutes passed before I was found sitting on the ground by the airplane with the battery master still on. The airplane was configured with the flaps up; throttle at idle; propeller control set for climb (2500 rpm); mixture cutoff; cabin heater half open; and cowl flaps fully open. This indicated that I was unsuccessful in re-configuring the aircraft for the descent. A fellow jumper who is a student pilot came by to turn off all the electrical components of the airplane. After about 10 minutes I was able to walk and talk which even included speaking to ZZZ Approach on the phone as they wanted to know the outcome of my emergency. Carbon Monoxide Poisoning.