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If you are sexually active and not on any form of birth control measures, then chances of pregnancy cannot be ruled out. Your symptoms (delayed periods, shorter and lighter periods, dizziness, headaches, tingly breasts, increased sleeping, tiredness) could be suggestive of possibility of pregnancy. Wait and watch for your periods. Look out for development of any other new symptoms suggestive of pregnancy.
If you suspect to be pregnant, consider visiting your doctor/gynecologist for a thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). Take adequate rest. Maintain healthy diet. Drink plenty of water.
Take care.