nausea, urinate often even in the middle of the night.

Hi,
Welcome to ehealthforum,
If you have come off your hormonal shot (birth control), and have been sexually active without additional protection, chances of pregnancy are possible (if your fertility/ovulation has returned back to normal). The symptoms of delayed periods, nausea, frequent urination could be few of the early symptom suggestive of pregnancy. 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 and continue with your prenatal vitamins.
Take care.