Infertility and Low Progesterone, any relationship???

Hi,
Im 30 yrs old,have a 6 yr old kid, im trying to conceive since 4 yrs, my dr. advised cerophene for 3 months but nothing hapnd, tubes are clear, U/S clear too, have pre menstrual spotting since 4 yrs, i saw on the internet that pre menstrual spotting is due to low progesterone, i went for the test on day 21 a year after having cerophene, it was 9.67, i think its low to conceive, can somebody suggest what shall i do?? pls help,, im v upset