question about CT scan and nodule

[gqmom]

So I had to go to the ER last night with a racing heart....turns out to be anxiety after tons of tests. I did have a repeat CT scan of my lungs which shows the same nodule that was there on my last CT about 7 weeks ago (then 4mm)...now is 3mm. I only had 1 chemo treatment 3 days before. Now I'm scared that it could be cancer and is shrinking because of chemo. Can nodules just shrink? Be measured diffferently (different hospital/machine/radiologist)? Now you can see WHY my anxiety earned my trip to the hospital!! Ugh....Anyone? Help!