Progesterone levels

I have just started having fertility investigations at my doctors. Yesterday was CD23 and I had a full blood screen. The receptionist has just called to say that everything was fine but that my progesterone level was borderline. The tests will be repeated next month and I'm going to see my doctor on Friday for a pelvic exam so will discuss the levels and results then. I'm just really worried that this means I won't be able to get pregnant. Has anybody else had this? What is likely to happen next if my levels remain the same?