I really did not notice any side effects with the Zyrtec alone. ...

I really did not notice any side effects with the Zyrtec alone. I have allergies to mice (which I work with in my job). The zyrtec really helped when I took it once a day at first. It stopped the sneezing and I did not feel funny (nothing I can think of). Then the zyrtec seemed to stop working after 12 hours, so I felt like I needed to start taking more of them. At one point I was trying to take 3 a day, almost like I was weirdly addicted to them? I went to the doctors b/c I knew something was wrong, and they put me on Zyrtec and Singulair cocktail. The Singulair has made me feel nausea, I have had extreme diarrhea, lower back pain and headaches. I think I want to try to stop taking all of the medicine and see how I feel! I don't know how bad the zyrtec is, but I know the Singulair made me sick!