Nausea after eating but negative pregnancy test and 6 days late for period. what could cause this?

Timing and technique: Of test. A home pregnancy test should be done 4-5 days after a missed period ( if you did it after six days, that is ok), using first morning urine and following the instructions carefully. If the test was done properly and is negative, the nausea is likely due to other causes, e.g., hormonal imbalcnce that may be causing irregular menses.