No period for month or two. irregular period. having strong an normal cramps on & off. plus very sore & tender nipples from the inside. why is this ?

Probably normal: Irregular periods occur in approximately 15% of women in any given cycle and have symptoms such as you are describing. Usually this occurs during a cycle where ovulation did not occur. More than likely, menstrual period will return to normal within a cycle or two.

Most likely normal: Common things occur commonly. As such, a pregnancy should be ruled out asap. Many things can affect one's cycle (e.g. Weight changes, surgery, stress, diet, etc..). The genito-urinary system is quite sensitive to these influences. The sore and tender nipples are symptoms of "tissue responsiveness" to ovarian/hormonal activity and, typically, are considered within normal limits.