I have itchy throat so i cough im 26 weeks pregnant does it affects my baby?

Likely not : As a rule, the only those illnesses (or meds) that will effect your baby are those that enter your body & spend some time in the blood. Examples:flu, measles, chickenpox, aids, etc. Any medication that you might take could affect baby, so consult your doctor when considering treatment. The placenta and bag of waters are a good cushion/filter for what can get to baby.