I've been having back pains, tender breasts, tired feeling, sleeping in the morning, and sometimes i feel so sick. what can be wrong? period is late

Get pregnancy test: One thing that is left out in the question is whether you are sexually active. I do assume that is the case and you need to first and foremost rule out pregnancy which you can check with a kit from any of the drug store and confirm from your doctor's office.if that is not the case you need to see your doctor to have a thorough work up and both of you should be able to come to a cause.goodluck.