Why does a wife experience light bleeding after sexual relations with her husband, having given birth to a son 8 years prior?

If sperm has been in contact with the vulva but no sexual intercourse took place, there is very little chance of getting pregnant. You acted so quickly by popping the "i-pill" that within an hour of the incident you lowered the risk even further. However, it may cause some mild side effects such as nausea, headache, or irregular bleeding.

Spotting can happen during pregnancy. Sex may trigger bleeding . Period indicates no pregnancy . . 

PID is an infection of the female reproductive organs, usually caused by STIs like chlamydia or gonorrhea. However, PID can also be caused by non sexually transmitted infection, like bacterial infections, medical procedures, or bacterial imbalances. Regardless of sexual activity, PID requires medical attention for proper diagnosis and treatment.

Urine infections and bladder troubles often cause pelvic pain and frequent urination. Common germs invade urinary tract parts, like the bladder or kidne­ys, sparking UTI. But irritants -- foods, drinks -- may also disturb the bladder, leading to the same issue­s. Hydrating well and dodging irritants helps relie­ve symptoms. However, see doctor for prope­r assessment and cure.

Ite's pOssiBle you're pregnanT.. Get a Pregnancy teSt to be Sure..

The probability of pregnancy would stay quite low if there was no ejaculation or penetration. Your PCOD (Polycystic Ovarian Syndrome) could be the reason why the cycle was irregular, and that is maybe why the period came early. See if there are any weird symptoms but most likely you are not pregnant. If you're truly concerned, testing for pregnancy and calming your mind by doing the test will be a good idea.