I go to sleep at night no problem. i wake up in the morning having to urinate and it feels as if my left side of my abdomen is full with lower back pain. when i urinate pain goes away. what is it?

See a physician to : R/o two conditions high in my list. Uti and urinary/kidney stones and diabetes (commonly complicating pcos). Does not look like a mechanical low back pain. A better history and physical very important.

See a urologist: Or a gynecologist. I am not sure why you are having these symptoms. One of the above specialists should be able to sort this out for you. Best wishes.