Vaginal bleeding. An uncalled pregnancy?

My girlfriend and I made love a week ago. Around a week before that (around 8th or 9th of march) she had her menstrual cycles. She took an ipill that day itself. However, she has been having urinal infection and vaginal bleeding now. Her bleeding, according to her own self is mild and not as much as normal menstrual bleeding. Also, she has abdominal and lower back pain. She suffered urinal infection around a year ago and with medication got well. Is this bleeding also a effect of urnial infection or a side affect of the ipill she took or is it a warning sign of an uncalled pregnancy? Is Ipill effective and what are the ways we can look to detect and stop this early pregnancy(if there is one) She is 19 years old and in a general healthy condition. Please help as this is worrying us beyond imagination.