Progesterone test questions!!! HELP

Im confused and need some advice. I've been having weird cycles and my OB ordered a CD21 progesterone test... Ive been tracking my O with OPKS and it says I ovulated on CD 18... so my blood draw was only 2-3DPO. I got my progesterone results back today and they were a 3.8... My OB is suppose to call tomorrow.. but if i did, indeed ovulate on CD18... shouldn't I wait until CD 24 or 25 to do a blood draw? Is it possible that my progesterone levels are still rising? Any advice or words of wisdom?