I missed periods for 2 months, my breasts have been heavy, I have mild joint pains. A few weeks ago I had pain in the middle of my back. Neg preg test?

Possible reasons. Reasons for missed / late period include: an anovulatory cycle in which no egg is released, marked v or ^ in weight; eating disorder; Over-exercising (endurance athletics), stress, travel, significant illnesses, oral contraceptives & other meds, Illegal drug use, breast feeding, hormone imbalances and medical problems (i.e., PCOS). Pregnancy is #1 reason.