I have all the symptoms of pregnancy but have a negative test what could be wrong?

Premenstrual: Syndrome can overlap in symptoms of pregnancy? Not sure. Is this the "missed period" you are referring to under conditions? Reasons for missed/late periods: low body weight, obesity, marked weight ^ or v, over-exercise, endurance athletics, breast-feeding, ^ stress, illness, eating disorders (bulimia or anorexia), anovulatory cycle (no egg released), travel, hormone irregularities, drug use, meds.