Due to kidney stones and a lung nodule, i had 4 ct scans over a 10 month period (2 chest, 2 ab/pelvic). seems i've weathered that storm but should i be concerned about the amount of radiation (around 42 msv) i received in such a short period?

There is a definite risk but it's difficult to estimate the consequence. I have had many sick patients who were in ICU where they have many CT scans done within a couple weeks but they need to be done. You should not lose sleep with that event but in the future you can request an alternative study without radiation if possible, e.g. kidney ultrasound can be used for monitoring kidney stone status.

Most CT scans now are done with low dose radiation. this amount of radiation will not harm you but it is always good to discuss this with the ordering MD before a test.