I have cramping back aches and i have a normal cycle im 3 days late and all 3 pregnancy tests came out negative. but i haven't taken one in the morning?

Occasionally,: There can be variations to your menstrual cycle. Normal could be every 21 to 35 days. If you have a negative pregnancy test, start keeping a menstrual diary. If your cycles continue to be irregular for the next 4 to 6 months, or if you have not had a period x 3 months (assuming you had prior monthly cycles), then seek advice from your doctor. He or she may want to do some testing. Best of luck.