Hello, I normally get my period like clockwork, within the same day or 2 every month, and my PMS is always the same - back aches and sore breasts. I had sex without a condom this past month but am in the birth control pill. However, my period is 4 days late, I ve had diarrhea and have been nauseaus all day today, to the point where I ve spent the day on the couch in between naps and have thrown up. I ve also been experiencing very severe stomach cramps all day, which I don t recall ever experiencing in any past monthly cycles.