A hefsek taharah needs to be performed prior to sunset, because then the first clean day can be considered complete, from its halachic beginning at sunset. Unfortunately, your hefsek taharah on day 8 was too late to allow you to begin your clean days on day 9. You can rely on this hefsek to begin your clean days the following day – day 10.
However, there is a possibility that the red spots you found did not invalidate your original hefsek taharah on day 7. If each individual spot was clearly smaller in size than a gris (roughly the area of an Israeli shekel or American dime), then that hefsek remains valid. Otherwise, if you still have the underwear, we recommend having the stains evaluated. If the spots did not invalidate your hefsek, since you did not perform any bedikot on day 8 prior to sunset, day 9 will be the first of your clean days.
For the future, we suggest performing a bedikah on the morning of a planned hefsek taharah, as a back up in case something causes you to forget later.
It is common for it to take some time to conceive. For women under age 35, up to a year is considered normal. However, if you are concerned, you should not hesitate to contact your physician for guidance. Sometimes small measures such as using an ovulation predictor kit, can help a couple pinpoint their fertile times to increase chances of conception.
Please write back with any further questions.