oxygen therapy intolerance

I have tried a couple of different oxygen therapies and have had trouble tolerating them. In the past I have had fatigue, candida, and parasite problems, although by using different dietary and nutrition programs, I am much improved now. When I try oxygen therapies I get bad headaches and aches and pains including pain around a tooth I had a root canal on. The last oxygen product i used is called cellfood although my previous experiences with others have been the same. I started very slowly with only a couple of drops a day and had trouble tolerating that. They recommend 24 drops/day. Can anyone shed light on this problem of oxygen therapy intolerance?