On Singulair only 2 days- can my irritabilty be from this?

hi! I was prescribed Singulair about 6 mos ago but when reading the online side effects, I never took it. Since then between 3 ENT appts and 5 tests at National Jewish Allergy and Asthma Center in Denver they discovered I have sinus issues, allergies and some asthma (at 42 a little confused on the asthma but whatever...) so they prescribed Singulair which I already had. I went ahead and tried it after voicing my concern about depression and anxiety (I have a lot of past anxiety in my life and some depression) and they said it was a minor side effect that was rare. So here I am 2nd day taking it and I could not figure out why I felt so irritated and mad at the world today- could it be the medicine? I am scared to keep taking it. Is there something else that works well that doesn't cause this! Thanks!