Thanks for the query.
Symptoms of nausea with unprotected sex on ovulation in the absence of contraception
I suggest you to get a urine pregnancy test done.
This is followed by transvaginal ultrasound
to be more sure.
If pregnancy is ruled out, other causes include thyroid, ovarian cyst
, stress and physical exertion.
You need to consult your Gynecologist for the same.
Hope this helps,