Dont want to get my hopes up/ Scared please help

I spotted from the 19th till the 26th and then it stopped. I was supposed to start my period on the 26th, but didn't and so far it seems like its not going to come at all.... I dont want to get my hopes up about being pregnant again. And also I'm worried about what if i am because i had to get a cat scan were they had to put dye in my body... If i am pregnant how bad would that have hurt the baby?