Thanks for the query.
like condoms have high failure rate (14%).
Moreover you have missed your periods by 2 days with symptoms of nausea and abdominal cramps. You could be pregnant.
I suggest you to wait for 5 more days and get your urine pregnancy
test. UPT is 98% sensitive when it is done 1 week following missed period. You can as well get your blood tested for Beta HCG
and transvaginal ultrasound
now itself to be more sure.
Hope this helps,