No period since late august. took pregnancy test abt 4 weeks ago. results were negative. mild cramping/bloating. pregnant? if not what could be wrong

Amenorrhea: A lack of period or amenorrhea can have several causes. Pregnancy is only one of them. I would schedule an appointment with your family doc or gyn to do a serum (blood) pregnancy test and TSH. The most likely cause is you haven't ovulated lately. However, a small percentage of women never have a + urine pregnancy test, hence doing the serum test.