Ectopic pregnancy, experiencing back and pelvic pain

Dear Ask The Doctor: Hi i am 17 years old and had sex with my boyfriend three weeks ago,the morning after i took the morning after pill.now i am experiencing back pain,shoulder pain and pelvic pain.i tested negative in a home pregnancy test,should i be worried?

Dear Alia: I do understand your concern for the symptoms you are experiencing. This is most probably due to dysmenorrhea or menstrual cramps. It is caused by high levels of prostaglandins which causes stimulation and contraction of the uterine muscles. Usually anti-inflammatory medication like NSAIDS are prescribed and will decrease the symptoms. If your symptoms do not improve even with medication, I would suggest that you speak to your doctor to rule out other causes of pelvic pain including endometriosis, adenomyosis, ovarian cyst, uterine polyps and adhesion. Signs of ectopic pregnancy will include light vaginal bleeding, lower abdominal pain and pain on one side of the pelvis which is unlikely in your case.