Am struggling to get pregnant again? what causes secondary infertility?

Many causes: I see that you are 44 years old. It is unusual for a 44 year woman to conceive. Most women that age who are pregnant have used donor eggs.

Fertility workup: See a gynecologist if you seem to have difficulty getting pregnant. Three main areas of testing will be suggested, after reviewing your situation carefully. Male factor is checked with sperm analysis. Ovulation is checked with hormonal testing and "tubal factors" like blockage and endometriosis are checked with imaging and minor procedures, like hysterosalpingogram, ultrasound and laparoscopy.