Cristina,
I am glad that you are getting IVIG on a semi-monthly basis, but if you're not feeling 100% normal, and you are experiencing episodes of muscle soreness and of lethargy and so on, the only *scientific way* to tell whether you are having residual, mild episodes of SCLS or not is for you to have your blood tested each and every time that you don't feel well.
If those tests were to reveal a level of hemoglobin that is above the normal range, then that would be a good indication that at the time you were tested you probably were having a mild episode of SCLS -- depending on how far off from the normal range you were, of course. And such evidence would then allow your doctors to adjust your dosage and timing of IVIG infusions for the purpose of eliminating said residual episodes.
If on the other hand those tests were to reveal that your hemoglobin was within the normal range, then you would know that at the time you were tested you probably had caught a cold or flu or something else from your daughter -- or whomever. (IVIG boosts your immune system, thereby helping your body to fend off certain illnesses, but it doesn't prevent them all.)
In sum, _you need to get out of the guessing business_ by having your blood analyzed whenever you don't feel normal. For that purpose, you can purchase a Hemocue device as I and a couple of other members of this community have done, in which case you can test your blood yourself and get an instant result any day, night, weekend, or holiday (see earlier discussions of this in the topic "Hemocue machine").
Alternatively, you can have your doctor issue a standing order for you to be tested for hemoconcentration at the nearest blood testing facility to where you live whenever you don't feel well. However, the downside of that route is that many such facilities are not open at night or on weekends and holidays, and besides they take many hours to give you the result.