Hi welcome to HealthcareMagic
Since the X ray
and urinary bladder
is normal, the kidney stones are absent , nothing major.... the urine test is also normal this rules out the UTI(urinary tract infection
).... While urinating if you in case sit down and urinate , then there will be retention of urine, other cause are urethral meatal stenosis, Hyerthrophy of Prostate
, the above problem is not much related to in experience sex.. Get USG of Abdomen and Pelvis to rule out any other causes, also you must be clinically examined for urine flow meter which will give report on volume of urine flow per minute....