why am I bleeding lightly off and on with no cramps?

Hi,
Welcome to ehealthforum,
The light bleeding with no cramps could suggest possibility of implantation bleed. The symptoms of frequent urination, pelvic pressure, abdominal cramps, headaches, fatigue, sore breasts, back pain, could suggest pregnancy possibility. Wait and watch for your periods. Look out for development of any other new symptoms if pregnancy is suspected. 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.