Why Can't I?

I want to Scream.. Cry.. I have been trying to have a baby for over 3 yrs now after my first miscarriage. I just don't understand why I haven't gotten pregnant. My Doctor just doesn't want to prescribe me Clomid.. He tells me that he wants me to track my periods on this app. and Get ovulation kit. which I already did.. I just want to cry and scream.. I see tons of woman getting pregnant while they are big.. sorry I dont know how to speak to someone about this.