It could be another urinary tract infection. You could try drinking cranberry juice or take AZO. If this does not clear up the problem, you should get tested for other causes.

Drinking cranberry juice may prevent a UTI, but it will not cure it. I don't know anything about AZO, so I won't comment on it. However, you should at least call your doctor and ask about it. Since you have a history of UTI, you may need stronger medication.

Don't let it go too long, or the infection could become more serious or even spread to your kidneys.

I do agree that you should drink cranberry juice (unless you are on blood-thinners) on a regular basis to help prevent UTI in the future. A lot of fluids in general is a good idea, as well. Also, make sure to always urinate right after sex--it helps prevent UTI, too. A lot of people don't know that.