If i got a postive opk test on cycle day 18 and doc took a preogesterone test on cycle day 28. is it to late to see if ovulated with blood test?

Close: Your Progesterone level should peak about a week after ovulation, and you will generally ovulate the day after the kit is positive. So, you are checking the Progesterone about 9 days after ovulation. It is close enough that the Progesterone should be fairly accurate.

Not too early: If your OPK is correct about ovulation on cd 18 a serum Progesterone will have risen within 3-5 days, so cd 28 is good.