No PMS symptoms this month?

So usually about 4 or 5 days before AF I get EXTREMELY emotional. About 2 days before I start getting bad back pains and know my period is almost here. This month I've had no emotional changes or back pain. My period is due in 2 days and The only symptom I've had is some strange cramping I've never felt before. I know implantation cramping is possible, but I've been careful in avoiding sex during my fertile window. Has anyone had implantation cramping and can you explain how it felt?