What Causes Pain In Lower Urinary Tract?

I have been treated for an yeast infection, ph inbalance, and still is experiencing pain in the lower urinary tract. I was first told I had UTI, then my gyne said no it was yeast and treated me with this little pill that did not work so they gave me the pill once again to no avail. So then cream medication for 3 days to no avail. I was talking to my niece who told me about AZO which see indicated that help her because she had a condition called IC and I looked it up and all the symptoms I am having points straight to this. I was wondering if I purchase AZO over the counter would it be safe?