As the ladies have said. Chances are you are not pregnant. Your period delay is likely from another cause... Stress, irregular sleep patterns, medications, etc. Can all off balance your hormones.
As for bacterial infections. It depends, if it is an interior infection then you will need some form of antibiotics. (make sure to use it all!)
if it's an exterior bacterial infection then you will need to use a cream such as adcortyl, aureocort, polyfax, terra-cortril ointment, etc.
Justin