There are a few other causes of frequent urination, besides urinary tract infections and pregnancy.
Diabetes is one of them (which might also be accompanied by other symptoms such as weight loss, gain, thirst, dry skin, sweet smelling breath).
The other is an enlarged uterus - which could be caused by benign fibroid tumors pressing on the bladder or adenomyosis which can cause the uterus to grow to two or three times its normal pre-pregnancy size.
Bladder infection, however, is the most common cause and should be treated right away to keep it from spreading and from having any more discomfort than you need.
Take care.