when should I test??

Patricia
I am not ttcing. i had sex on jan 17/cd 13 (2nd to last day of ovulation on calendar) and he pulled out. I am now on cd 26. My period is irregular, and it says it is supposed to start tomorrow but i have not had any pms signs. I dont keep track of my cm but sometimes when i am sitting on the toilet some thick, yellowish discharge hangs down but when i did a cm check it was dry. Any thoughts? Scared i could be pregnant.