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.