you didn't mention your age as the cause of symptoms changes depending on age,
your symptoms could be because of hormonal fluctuation, in case of regular periods by this time urine test can detect the pregnancy,
if you are having irregular periods
better to consult gynecologist once and go for blood test
for pregnancy once which will rule out the possibility of pregnancy, then you can go for physical examination and ultrasound
examination, if your doctor suggests hormonal evaluation like estimation of levels of estrogen, progesterone
, LH, FSH and prolactin
etc can be done, with this workup the possible cause can be find out and treatment can be taken accordingly.