Hi,
Welcome To HCM & Thanks For Asking Your Query Here
As You had unprotected sex and its been 2 weeks so your
nausea may be related to
pregnancy but as you said you have taken one Birth control pill after sex that day means your nausea is most probably related to the pill you have taken (as Nausea is one of the most commonly reported side effects of birth control pills)
according to your medical history you don't remember that whether you took your Birth Control pill that day so you took one pill after sex this means it is highly possible that you might have taken double dose of birth control pill that day and that's why you are facing these side effects intensively
To prevent nausea, don’t take your birth control pill on an empty stomach. Instead, take it after dinner or with a snack before bed. You can also take an over the counter
antacid medicine like pantoperazole about 30 minutes before taking the pill. This may help keep your stomach calm.
if you use emergency birth control pill than Before using the pill, speak with your doctor to see if an anti nausea medication can also be used. They may give you a prescription for an anti-nausea medicine such as metoclopramide
if your current symptoms do not subside by given instructions i would strongly suggest you to see Your Gynecologist for further evaluation of issue
I hope it help
Thanks & Get well Soon