I am on birth control with 4 placebo days, i am coming onto my 5th day with no period. i didn't have sex this month, but i did come into contact with dried precum. what are the chances of being pregnant and where is my period?

Very low: Assuming you have taken your pills consistently and have not been on other medications, particularly antibiotics, your risk is extremely low. On the pill the lining in your uterus tends not to build up much, hence your period will be lighter and sometimes disappear entirely. It is not "lost" and nothing is being blocked from coming out.