Hi, I dont think you belong to the infertile category since you managed to conceive before. My suggestion is to use a good ovulation kit like clear blue or guardian brand and try to obtain your ovulation date.
If you do go and see a fertility doc then he will monitor the growth of your follicles in the cycle. And if really no ovulation by day 16, he can give you a pregyl injection to ovulate. I have seen Dr Cheng at Thomson Medical Center but he is a male. Hope my info helps.