Light cramping??

I am a week and 2 days late on my period and every test I took was negative.( I last took a test on Monday.) I keep having light cramping but no period. Also been feeling kinda sick to my stomach. And my nipples are super senstive and I have been tired but it could be just getting back to work after a week long vacation. I work with toddlers so they are pretty exhausting. Has anyone else had this happen and later found out they were pregnant? Or what is going on with my body?