Not interested in sex, sharp pains in pelvis, periods only twice a year, sudden sweating. Cancer symptoms ?

Your symptoms are quite unlikely due to cancer, although i would have preferred to know more details about the family history of cancer that you speak of, which part of the body, how many relatives, which relatives, their outcomes. Anyhow, as i said, your symptoms dont seem to be due to cancer. Rather, you seem to be suffering from abnormal functioning of the thyroid gland. I suggest you undergo a thyroid function test ( its a simple blood test done empty stomach at any lab) and if they are abnormal then they will need correction based on the abnormality. Also, that will explain all your symptoms which will then get relieved gradually with time. At the same time i would suggest you to undergo an ultrasound of the abdomen and pelvis just to be sure your reproductive organs are alright. Only after these tests can a further course of action be decided upon.