26 weeks and cramping..

T

So I was in class today, couldn't even make it an entire 20 minutes without running out and BAM I'm instantly feeling dizzy, getting horrible hot flashes & cramping.. I came home an hour ago & im having worse cramps than I did early, like they are very sharp pains.. where I started crying.. whenever I sit up or walk to use the bathroom I'm beyond out of breath .. my chest starts hurting.. has this happened to anyone before ??