I have reoccurring uti's and kidney infections. My doctor has prescribed me nitrofurantoin 50mg tablets. Now I have the normal side effects of headache, nausea, loss of appetite, dizziness, confusion, etc. But for the last couple of days I have been having lower abdominal pain and lower back pain that often sticks to the left flank. I am not sure if this new pain has to do with the medication or if it could be something else. I have read the side effects, and read reviews from others and haven't found this. Before you ask me if it is my period, nope it is not. Also, it is not a cyst. I have had them in the past and they don't feel like this, nor do they last this long. I have had stomach ulcers in the past from medications for uti's and my kidneys. But, it doesn't feel like that either. 

Please help, I am not sure if this is serious. 


Thank you.