There are several issues to consider in this situation. There are several conditions that can cause symptoms. Certainly, urinary tract infections are very common, but anyone that has been struggling with persistent or recurrent urinary tract infections for 6 months should seek further evaluation. When there has been a failure of the usual antibiotics, it is always reasonable to perform a urine culture to determine the germ that is present and what antibiotics kill it the best. There also should be an evaluation to determine if there are any other underlying conditions that predisposes to having an infection.
It is also possible that there are other conditions in the urinary tract that cause similar symptoms without an active infection, such as interstitial cystitis. There also may be similar symptoms caused by infections in the female genital tract.
Ultimately, it would require an appropriate evaluation to determine the cause of your problem. It is generally better whenever there is a condition that causes chronic or recurrent problems to be followed by a doctor that will become familiar with your situation. However, it also may require more of an evaluation than can be done by a family doctor. but a family doctor will be able to refer you to the appropriate specialist.
Yes, it is possible that you could be having recurrent infections from intercourse, although it is more common in women that have a sudden increase in sexual activity, such as on a honeymoon. Recurrent urine infections from birth control is not common, but it is possible, and since it occurs infrequently, it is difficult to differentiate the effect of sexual activity from the effect of the drug. It is also possible to have an infection of the female genital tract that is not sexually transmitted.
Yes, a vaginal infection can cause urinary symptoms, by causing irritation of the external genitalia, which includes the opening of the urethra. Some vaginal infections are due to sexually transmitted germs, such as trichomonas, but some germs do not require sexual activity, such as the yeast. Yeast vaginal infections are more common in women that are sexually active, but it does not require that there be sexual activity. Your family doctor would be able to determine whether this is a urinary tract infection and also can typically determine if there is a vaginal infection or other infection of the female genital tract.