late af with Clomid????? anyone pleasseee

Okay I don't know everyone's situation taking Clomid, I'm guessing most of you are irregular bc of pcos, but I'm very regular and I'm taking it for unexplained fertility and it's my first cycle down, I'm regular and was due on the 30th, did take a Walmart test on the 27th which was negative, is it normal to be late if ur regular? 
I don't feel like paying for a FRER for another millionth Bfn, thanks