PCOS, Metformon and 18days late

hi all! i have pcos and hoping for a second baby. im currently on metformin (it helped me get

pregnant with my first baby) and now im 18 days late but testing negative. this is the longest my period has been delayed and now scared that a chance of a second baby is not possible. my OB wanted to do a saline hysteroscopy and said to call when my 1st day of my period arrives but it still hasn’t happened. anybody on the same boat? :((