You have suffered from "chronic" CO poisoning, exposure to "subacute" levels of the poison -- not high doses which kill within minutes or hours. After exposure (whether on 1 day, 2 days, 3 days), in only 4-6 hours, CO moves from the bloodstream into the tissue where it continues to attack, forever, the brain, heart, lungs, and central nervous system.
It will stay there until you get on daily oxygen. The prescribed amount is 2 liters per minute, for 2 hours per day, lying prone, for four months. This continued daily oxygen therapy drives the CO out of the tissue.
If you smoke, you need to stop. Vitamin C helps substantially as well as the B vitamins. All other vitamins and herbs should be discontinued because the body produces CO naturally (it fires up/triggers the nervous system) and many of these other items can cause the body stress, and stress is a big CO producer.
You are already experiencing "long-term effects". You won't be a candidate for hyperbaric because the MDs won't find it in your bloodstream since it's already in the tissue.
I highly recommend that you contact Albert Donnay, a private consultant and a Housing and Urban Development (HUD) advisor. His nonprofit is mcsrr.org.
Most MDs do not know how to treat chronic CO poisoning, knowing only "acute" and the last symptoms on the list which are convulsions, coma and death.
For Vitamin C, the product Emergenc-C, available in any health food store, is excellent too since it has 1,000 mg of Vit C, as well as the B vitamins.