Clomid questions

A
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 levels...do 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.