We appreciate your concerns about secondary infertility. The amount of time it takes for a woman to conceive another child after giving birth varies from woman to woman, even within the same family. Nursing can also delay conception.
If you have not been using any form of contraception and your menses have resumed, then you should contact your physician at this point with any concerns. Reaching out to your physician is a proactive step you can take to gather more information and allay your worries.
If you’d like to talk out your concerns further, you may also find it helpful to consult a Yoetzet Halacha Fertility Counselor. This is a free service, details here.
Please let us know if we can be of further assistance.