Which one will be better for me progesterone test or HCG test?

We are ttc since 6months. i went through HSG on cd 9.my gyn told me in order to find out the progesterone level i can do a blood test.she told me to do it on cd21.my cycle is of 30 days and i have ovulated on may 30th.please tel me when should i check my progesterone level.as i have hope that after doing HSG the chances of pregnancy is high.so should i check my progesterone or HCG?