Pregnancy symptoms vs pms symptoms

I have really bad endometriosis.the doctor told me it was 98%that I would never have another child. I have 4 BTW youngest is 8. Even though I get pregnency symptoms every period I'm freaking out. I have been nausea for about a week now and still 8 days before my period should start. Also sore breast and now today I started cramping. I took a test a couple of days ago and it was negative but I'm nervous and really just wanna know. Ugh the things mother nature does to us women. Anyone else ever go through this so much before there period?