Getting worried.

Leila
I had sex about a month ago. It wasnt planned sex and we started off without a condom for a little bit and then i remembered i had some so we used that well.. Now ive missed my period 5 days now after we had sex a month ago. I have really bad cramps on and off throughout the day. Could i be with child? How could it happen if the condom didnt break. Im just so confused. Tell me what u think..