Are you a male or female?
Do you have fever
? Is there any pain associated?
I suppose there is no history of recent trauma ?
Pulsating sensation has to properly evaluated.
Get a couple of investigations :
1. Complete blood count
2. Routine microscopic urine examination
3. Urine culture and sensitivity
Get these tests done and see a physician for clinical evaluation.
Because of the throbbing sensation it might be some pelvic abscess
or some pelvic inflammatory disease
in females or some prostatic pathology in males.