Thanks for the query.
Ideal size of follicle at the time of rupture is 18-22mm. Since follicle is not developing in your case i recommend you to get your blood checked for hormones-Thyroid
, FSH, LH, Estrogen
If everything is normal, there is nothing to worry. Reduce your weight if overweight
, eat fresh fruits and vegetables. Keep yourself active and stress free. Chances of conception are good for those who already have kids.
Hope this helps,