TTC- progesterone levels?

So my husband and I have been TTC on and off for about a year. We ended up at a fertility specialist and he has been checking my progesterone levels. I'm 5 days from when I'm supposed to get my period, but I seriously think this is the month because I've been nauseated and last week I was throwing up for no apparent reason. Do progesterone levels (mine was 10.83 CD 22) rise when you're becoming pregnant? Dr. Scheduled me to check again next week on the day I'm due for my period. He said even if i bleed to still get a blood test for HCG and Progesterone. What is the point of checking this again next week?