Clomid help

This is my 5th cycle but this is the first time that I have been having all these symptoms. I have only been having 26 day cycles since on clomid. Today is cd 28 and no true sign of af showing up. I took a hpt and it's negative. But I have been nauseated, gassy, bloated, achy feeling like coming down with the flu. Typically I have really bad cramps before af and nothing. Has anyone had this go on and not be pregnant. I am concerned bc at this point I feel like if I was pregnant it should be showing up by now. Any thoughts?