PMS symptoms but no period??

Okay ladies so lets start off with I have a VERY VERY REGULAR PERIOD. My period comes on the 28th day of every month and I'm never late (sometimes a day early) but never late. Only time I've ever been late so when I had a chemical pregnancy 3 months ago. We've been ttc and I took opks this month. I've been getting negative pregnancy tests everyday since 5 days before expected period. I was supposed to start today. I even got a headache last night (I always* get headaches the night before my period is due and I ALWAYS start in the mornings, never start in afternoon or night time) well this morning I woke up and had mini cramps and even down my left leg like I usually have when I get my period but I'm not bleeding at all. What does it mean when you feel like your about to start but don't? By now I would have started. I know I sound crazy but women know their cycles and I know when I'm about to start. If I'm having cramps like I'm going to but don't could this mean I'm pregnant? When should I test again? Mind you, whenever I start my periods in the morning I get cramps that sometimes I can't even bare to handle and have ended up going to the er a few times because my cramps have been severe but this time they're small cramps nothing like I usually have.