Could you be pregnant if while taking Estrostep everyday along with cold medicines and your period was very very light?

Hello, If the cold medicine you are referring to is a Antibiotic then there is a risk of pregnancy as Antibiotics can interact with the working of birth control and lower its effectiveness at preventing pregnancy. Continue taking birth control but see your Doctor for a pregnancy blood test or perform a urine pregnancy test if you had intercourse 3 weeks ago. Take care, Trisha x