What Causes Delay In Periods And Slight Spotting After Taking Loestrin 24 Fe?

hi i am 22 years old, and just had a baby. he was stillborn much to our dismay, and four weeks later my ob put me on loestrin 24 fe. i took it the following sunday. i cant remember the antibiotic that was prescribed to me toward the middle of the month, but i had to take it for three days. i took a pregnancy test two weeks ago, bc i had no period at the start of my placebo pills, and it was negative. now i have a discharge with a slight bloody tinge to it, and now i am starting to worry, bc it is to soon for me to be pregnant. should i take another pregnancy test?