Emergency hormonal contraception like plan B can alter the hormone balances that occur during a normal menstrual cycle. Symptoms may occur that are confused for pregnancy including breast tenderness, nausea, changes in urination and cramping. In addition, the short term use of these hormones may induce another bleeding episode, such as the one you describe. Other women may have delayed menstrual bleeding from the effect of the hormones. Discomfort when urinating may signify the early development of a bladder infection. Urinary tract infections that have set in usually do not get better without antibiotics and symptoms may worsen. Increased water intake may help, as can cranberry juice which can help alter the pH of urine to suppress bacterial overgrowth. A short course of antibiotics may hold off the development of a full blown urinary tract infection. You and your primary care physician or gynecologist can decide if this is appropriate for you. Home pregnancy tests will usually be positive ten days after conception. However, plan B is very effective and pregnancy is unlikely if the medication is taken as directed. I hope this helps answer your questions. I am available for any further questions that may come up for you.