What Causes Menstrual Cramps Mid Cycle With Vaginal Discharges Pain?

i'm 22 years old and i've been having menstraul cramps eventhough i'm not on my period.. i also have a slightly discolored vaginal discharged its white with a yellowy green hue. there is no smell and it does not itch or burn. i've been tested for stds and yeast infections and i've come up clear. the pain comes and goes but the discharge is always there. there is alot of it and its very uncomfortable. this has started about a year ago.. i'm on the nuvaring and have been for about 2 years now.. what could this be?