Common complaint of young women.
Jes is right profesional secrecy may help you to avoid your mom to know you had sex.
But i think you are worried about the relation between sex and UTIs (urinary tract infections).
UTIs are incredibly common between females, the reason is very simple. The tube that your bladder use for voiding (the urethra) is aprox. 5 cm long on a grown up female, it is almost perfectly straight and in close proximity to an humid and hot cavity, and to the rectal exit.
Many factors can facilitate the contamination of urethra and bladder. Sex is just one more of them. UTIs are not considered sexual trasmitted diseases (STDs), unless a test or the symptoms indicate the prescecne of a nasty ST bacteria. Examples: hormonal changes, bad poop cleaning technique, non natural fabric underware, jeans (those that are used tight).
Sex may help an infection because during intercourse the male organ acts like one of those manual water pumps by compresing the urethra against your pubis bone. This can facilitate some liquids and debrids to be sucked into the urethra.
So relax, be honest with the doctor. Give him or her a try. Remember that doctor-patient secret is by your side. Trust your doctor.