light to dark, heavy to light, positive and negative?

Hi,
Welcome to ehealthforum,
The bleeding that you describe could be the probable implantation bleeding. The urine pregnancy tests rarely show false positive results, and these should always be done on an early morning first urine sample to get accurate results (pregnancy hormone HCG is believed to be in highest concentration in this sample, and you should avoid lot of fluid intake and caffeinated beverages in the night before taking the test). The symptoms could suggest chances of pregnancy. Wait and watch for your periods. If pregnancy is suspected, look out for development of any other new symptoms suggestive of pregnancy. If periods do not start within 10 days of expected period dates, or if you get abnormal periods, or if you suspect chances of pregnancy, consider visiting your doctor/gynecologist at the earliest for thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Take adequate rest. Drink plenty of water. Maintain healthy diet.
Take care.