Yes you can very well transfer it to your boyfriend through sex.
The urinary tract can be infected by bacteria in two ways:
The methods to prevent UTI are:

The most important method of preventing such infections is to practice good personal hygiene. Always wipe from front to back after a bowel movement or urination and keep the skin around the anal region clean.

Drinking plenty of fluids each day also helps in flushing the bacteria out of the urinary system.

Empty the bladder as soon as the urge to urinate occurs.

Taking of foods rich in Vitamin C such as amla, citrus fruits and juices helps to reduce the number of bacteria that might be harmful to the urinary tract.

Enjoy Life