Undecided on clomid/letrozol

I've had 2 miscarriages since September and my OBGYN referred me to a fertility clinic.  We now know I have low progesterone, and 2 blood clotting conditions.  I didn't get pregnant on our first month with the clinic and now my doctor is talking about a clomid or letrozol try for the next month.  I'm torn because I've gotten pregnant naturally (on the first try both times) and I don't want to add a medicine I don't need.  But at the same time I am SO ready to have a healthy pregnancy that I'm reluctant to turn down anything that could help make that happen sooner.  Any advise??