Period about 1 week late and at the start, I had abnormally heavy dark brown blood which lasted 2 1/2 days. It's lightened up but still brown. Also having right-sided dull crampy pain which seems to travel to my low back. Today I've felt lightheaded, not right, out of focus and a little nauseous - seems to get slightly worse when in a moving vehicle. I had Essure about 3 years ago - have had the dull low back pain since, also with problems urinating - bladder doesn't seem to empty unless I force it (if that makes sense). What can be wrong??