Hi there ! The pain in your left side rib cage could be due to respiratory tract
infection as described in your history and also due to a possible infection of the pleurae.
The burning sensation while passing urine is possibly and rightly due a urinary tract infection
, which occurs not infrequently in sexually active females. This could be associated with infection of the pelvic organs giving rise to pain in the back and lower abdomen. The treatment for both needs proper antibiotics.
The irregular bleeding could be due to your contraceptive
plan B , but a chance miscarriage
can not be excluded. Any foreign body in the uterus may give rise to such symptoms.
You should go for routine blood and urine tests, along with an ultrasound
of the abdomen and an x-ray chest if advised by your physician and only after excluding pregnancy. Good luck.