My partner and i have been trying to get pregnant for over a year, he has already got a daughter. is it my fault? i have irregular periods!

Potentially yes: Having irregular periods can indicate that woman is not ovulating on a regular basis, or that the corpus luteum, which forms after ovulation, is not producing a sufficient amount of progesterone for a long enough period of time. The work up should start with seeing a regular gynecologist, who then may refer to a reproductive endocrinologist/infertility specialist.

See OB: You should discuss this with your OB. He/She may recommend a fertility specialist for you both to be checked out.

Time for consult: If you have been having unprotected sex with your partner for more than a year & not conceived, a workup at a fertility center may be the best way to find answers. Both you & your partner will need to be evaluated. Your regular OB can sometimes start the process but the center can study you both & provide information on assisted pregnancy if needed.