I've been bleeding brown blood since tuesday, 2 weeks exactly after my last period. the bleeding stopped for a bit this morning but has now returned. i have a dull pain in my lower back and feels like a stitch in my side. i'm a bit worried, help?

If you are not on low dose BCP's, and pregnancy is possible, this kind of bleeding may indicate a pregnancy outside the uterus (ectopic), especially with back and side pain. Obtain a serum HCG test to be certain about pregnancy, and see your gyn physician if the test is positive. If on bcp's, missing or taking the active pills late, will start breakthrough bleeding.