I've been having pms symptoms (acne and some cramping), but my period hasn't come

I'm 18 and my boyfriend and I had protected sex (well kind of, he was only in me for about 15 seconds before I changed my mind about the whole thing and told him to stop). He never ejaculated and the condom did not break. My periods have always been sort of irregular. I missed my period last month before any of this happened too. 

We haven't had sex since then or before then. Everything else we do is oral and manual sex where we never have an gential to gential contact and his semen never comes near my vagina. 

The past couple days I've been having pms symptoms (acne and some cramping), but my period hasn't come. I'm not sure if it's because I'm under a lot of stress right now.