What Causes Irregular And Short Periods And Pain In Breasts?

hi well my periods have had irregular periods for three months now and well bk in april i done preg test and it come up pos and neg with different test and been testing and stayed neg now, i have had pains in boobs for 3weeks now and now left arm pit hurts, i have a period every 5 weeks roughly now and only 2days long been like that for 3months, ive been tired alot and moody.