My period was supposed to come Monday. I am sometimes a day or two early, but typically 28 days and never late. Never been pregnant, diagnosed with infertility, had failed treatments, so I doubt I'm pregnant. I took a test Wednesday and it was negative. I've been hesitant to spend money on another test, because I'm sure the second I do my period will start. Any clue what could be causing this? I Should I test again or wait longer?