What Causes Infertility Having Regular Periods?

I have been trying to get pregnant for a while now but am unable to conceive. I am in my mid thirties, had both polypectomy and myomectomy last year, I do not think there is anything wrong with my fallopian tubes, I ovulate regularly, I have never had an STD, I do not use any contraceptives, but am simply not conceiving! Please advise.