Clomid questions

How do doctors decide whether to prescribe clomid cycle day 3-7 or 5-9. 
Also, my progesterone level this first time was only 4.53 (BUT I started AF on my own today on cd 33 so that's positive. Typically I need provera after 70 days...)
Would going up to 100mg help the progesterone they ever prescribe progesterone AND clomid to better conception chances? Just wondering what y'all have experienced before I call my doctor and one of those questions winds up being totally ridiculous lol.