I know this should be simple to work out but I have gotten myself all confused

According to my LMP i would be 5 weeks and 6 days today but as i know that is based on a 28 day cycle and I have 32 day cycles should I subtract 4 days and say I am 5 weeks and 2 days? I have been going with the subtraction of 4 days but my Doctor keeps saying no it is counted from LMP regardless of cycle lengths but I cant see how this could be accurate for people with longer cycles.