i am 18 years old and i have been having severe lower back pain for about 2 months now. after massaging my lower back, i found a lump that is in between marble and golf ball sized. it moves around quite a bit and is sometimes very painful to the touch. i have also been very fatigued and get tired very easily, which is not like me at all. i have had some back problems in the past, but nothing that has hurt this much. what could it be?