Are Missed Menses, Cramping And Spotting Related To Pregnancy?

Im 16 years old. And me and my ex boyfriend which was my boyfriend at the time had sex on July 13, I missed my period which i was suppose to have last week. And i been feeling cramping in my lower stomache. I've been having heartburn, acid relfex, metalic taste in my mouth, spotting, tired, legs get weak, dizzy, and lower back hurts. Is this possible for me to be pregnant?