When venturing out in new techniques, it is understandable that one might think that getting a cold or not feeling well might be some type of cleansing effect. As far as I know, this would not occur with EFT, but if I am wrong, someone please jump in. Depending on the person, several layers may have to be uncovered to get to the root of the belief.
My advice is to continue doing the tapping, at least twice a day and if you feel issues coming up, for example, fear, insecurity, so on and so forth, immediately start tapping. It does take practice, but notice the relief as you tap. As the days go on, you will notice yourself feeling better and you will notice your life changing for the better.