Thanks for the query,
Many factors are responsible for selection of dominant follicle.
Interaction between extra-ovarian and intra-ovarian factors that determine the fate of the follicle and the quality of the oocyte
imbalance between LH and FSH results in atresia of follicle without it being dominant.
PCOS is another condition where there are many small follicles and none being dominant.
Treatment is to start gonadotrophins in first half of the cycle.
Followed by folliculometry.
Reduce weight if you are overweight
Eat balanced diet,
Have a stress
Hope i have succeeded in answering your query.
You could write to me for anytime for further clarifications,