Thank you for your query.
FIrstly, with unprotected sex, you always run the risk of a pregnancy
An early pregnancy, a failed pregnancy, an ectopic pregnancy, all could present this way.
, stress, thyroid disorder
, polycystic ovaries
, frequent travelling, weight changes etc could present this way.
Cervical polyps, endometrial polyps, cervical growths all could present in this way.
I think you should consult a gynecologist to know the reason for this kind of bleeding.
Being on hormone containing medications is also a risk factor.