Once a woman ovulates, she is fertile for approximately another twenty-four hours. In other words, between mikveh night and the following night, you have a number of opportunities to have relations and conceive. Given that there are differing opinions on what combination of timing and number of attempts optimizes fertility, it is not clear that halacha is constraining your fertility in this case.

It is important to realize that, even in cases where there is no halachic factor, it can take several months to become pregnant. That you became pregnant so soon after marrying was fortunate, and is a good indicator of your fertility, but it does not suggest that it will only take two months each time.

In terms of halacha, in order to minimize any effect, the major step to take is to ask questions about attempted hefsek taharah and bedikot in order to make sure you are not extending your time in niddah unnecessarily. Even a hefsek taharah need not be completely clear. In addition to the above, you may also find it helpful to consult a Yoetzet Halacha Fertility Counselor. (This is a free service, details here.)