4th miscarriage- what to ask ob?

Natalie • July 21 💚 Feb ’20 💙 March ‘18 💙 Dec ‘15 💙🧩 4 miscarriages 🌈
After my second miscarriage, I went to my OBGYN. He rx'd low progesterone and advised I begin when I got my next positive pregnancy test. Seemed to do the trick because I went on to have a beautiful son, now 16mos. 
I had another MC last November...I didn't start progesterone in time. Just got a BFP Thurs, started progesterone, now bleeding and feeling awful, dizzy, nauseous. My 4th MC 😔
What questions should I prepare for my next OBGYN visit? I am worried about chromosomal abnormalities (my son has a rare deletion w/special needs. We were told by his geneticist that it was NOT hereditary, but I still worry - should I request tests? Which ones?). 
My MCs never made it past week 8, the most recent less than 5w, so very early. Would it be better to start progesterone after ovulation instead of waiting for bfp?