I am not a doctor but you may have a kindney infection they will cause pain in your back and your stomach I have something called Endometriosis it can be vary painful at times it is considered one of the most hidden disese a women can have go to a website on it and see if you have some of the symptoms some women have none and like myself some women experience all kind of syptoms I hope this helped for me some days I have no pain and other days I am in alot of pain the cramping is horrible
OHH!!..well then i'm not sure. My friend had a lot of problems with her overies..and had the really bad cramps and the doctor put her on some kind of pill (sry i dont much about it lol) but it cured it for her. I would just ask the doc!
forgot to add I have taken 2 test with negative results
Well i'm not a doctor..but..a late period is a sign of pregnancy..i'd just take a test and see what it is. Good Luck!