Welcome to HCM,
You are trying to conceive, but not doing intercourse on proper days. In a normal regular menstrual cycle of 28 days, ovulation is expected to occur on 14th day of menstrual period's first day, which can be further confirmed by using ovulation prediction
kit. To increase the chances of fertilization of egg, you should have sexual relations on the day of ovulation & for a few days thereafter. To improve quality of semen you should avoid sex during remaining days. Your husband can get his semen also examined to rule out any fault on his side.
Wish you good health & early conception,