Unprotected sex during ovulation time has high risk for being pregnant. You undergo blood test
for beta-hcg & TVS scan at the earliest to rule out pregnancy.
Other reasons are hormonal imbalance, ovarian cyst
, over wt/ loss, irregular diet habit, stress/ anxiety, thyroid disturbance etc.
Here, you need to consult with gynecologist for relevant investigation like pelvic ultrasound
, hormone assay etc and take suggestive measures accordingly.
Take some anti spasmodic (like Drotin) to get relief from abdominal cramp
. All the best.