Fertility Help

let me give you a little info about myself. I am 23 yrs old and he is 31. i have a soon to be 4 yr old son and had zero trouble getting pregnant with him. went to the Dr in June and she said i was insulin resistant and prescribed me 500 mg of metformin four times a day, prenatal, and prometrium 200 mg daily for cycle days 15-25. has anyone had any success with these? I know she said it would take some time but after six months you start to lose hope. I am also afraid that it has messed up my ovulation BC i didn't get a positive home ovulation test. I am just confused and dont want to start worrying if there is no need for it!! She didnt put on clomid so I am hoping that it is a good sign but i am just unsure. I do not have PCOS and I havent been on birth control for over a year.