Will try to help explain. I have a microbiology/chemistry degree and actually helped manufacture diagnostic kits for Toxoplasmosis years ago. So hear goes...
the only way that IgG antibody levels can indicate if you are having a reactivation is if you have the levels charted over time to see if they are going up (eg. on going infection) or coming down (clearing of infection).
Wish I could draw you a map of a typical antibody response. IgM type antibodies are made by your immune system as a second level of defense. They are less specific to the "germ" and spike quickly in initial onset of infection then drops off quickly (could be days/weeks/months, depending on your body and/or germ). IgG type antibodies are your 3rd defense. They are much more specific (i.e. sticky) to the germ and are used by your body to capture the germs and deliver them for destruction. IgG concentration peaks sometime after the IgM antibodies indicating that your body is clearing the body of the infection. Once the infection is in control the IgG level drops lower to maintain immunity/control of infection.
I am not sure if the number you are giving me is 17 IU/mL (infectious units/mL). If it is.... this is a low positive. Thus the likelyhood that you have an active infection at time of blood draw is low. Or.... in could be that your immune system is losing the ability to make good sticky IgG antibodies (which has been theorized in CFS).
In a healthy body, Toxo levels are either cleared or kept very under control so that it does not spread and infect tissues commonly in gut and brain. Immunocompromised individuals are at risk (HIV+, transplant recipients etc..) because their immune systems are not functioning which allows the Toxo to travel from gut region and survive as cysts in others tissues such as the brain and muscles. I could see this being a concern because many immune abnormalities is observed in CFS and thus people maybe at more risk.
Something to feel better about.... being positive to Toxo is not uncommon. Depending on region you are living and culture eating norms, Toxo has infected from 20% to approx. 80% of population (seen in areas that eat undercooked meats, European countries).
Hope you are feeling better soon!