progesterone levels on clomid

[ks78]

I have been diagnosed with PCOS a year back.
I am trying to conceive for the past 2.5 yrs. I am on the 3 rd cycle on clomid 50 mg.
1st cycle clomid - progesterone level was 27
2 nd cycle clomid - progesterone level was 22
3 rd cycle clomid - progesterone level was 12

My doctor says I have ovulated on all my 3 cycles on clomid.
But I read somewhere that in normal cycle progesterone level over 10 means ovulation has occured
but on medicated cycle the progesterone level should be more than 15 for ovulation to occur.

My 3 rd cycle on clomid has a progesterone level of 12.

I would like to hear from experts whether progesterone level of 12 indicates ovulation on medicated cycle.

Also I would like to know what is causing the progesterone level to lower in each of my clomid cycle.
Does that mean , the next cycle on clomid 50 mg is going to result in a progesterone levels < 12.

I asked my Doctor and she says its normal but she is not able to give an explanation for that.

Any information on this would help me a lot.

Thanks in advance.
- KS