Thank you for reaching out to us.
Your hefsek taharah from Friday remains valid, even though you omitted bedikot the following two days.
However, the bedikah of the first day is a critical step in beginning the count of seven clean days. Omitting it delays the clean days and mikveh immersion. Your bedikah on Monday established Monday as the first day of your clean days. This puts you on schedule for mikveh immersion Sunday night, instead of the originally anticipated Friday night.
The reasoning behind this is that bedikot are supposed to be performed on each day of the clean days to confirm that there is no bleeding, and as an act of counting that demonstrates a woman’s awareness that she is in her clean days. In some cases, as when it is painful for a woman to perform bedikot, the number of required bedikot may be reduced to the hefsek taharah and one each on day one, day seven, and an intermediate day of the clean days. Day one and seven are considered especially important, because they are the beginning and end of her count.
If performing bedikot is difficult for you, we might be able to help find ways to improve the experience, if you provide us with more details. If your delay in performing bedikot emerged from difficult circumstances, then it could also be important to get back to us, because in some very extenuating circumstances (e.g., cases with shalom bayit and fertility concerns) there may sometimes be room for greater leniency with bedikot.
Please let us know if we can be of further assistance.