You do need to inspect your white underwear during the clean days. However, not all stains will invalidate the clean days.Stains found on your white underwear that are individually smaller than a gris (the size of a US dime or Israeli shekel) may be disregarded and do not invalidate the clean days. Stains larger than a gris may be brought to a rabbi for evaluation since not all shades are problematic. So too, stains of any size found on an internal bedikah can be brought for evaluation.
If you have been bringing these stains for evaluation and they are problematic, you may reduce the number of bedikot required during the clean days to one each on days 1, 7, and one additional intermediate clean day.
You may change your white underwear more frequently to prevent stains from accumulating to the size of a gris. This way, stains smaller than a gris may be disregarded. If, despite this, staining is still causing you to restart your clean days, you may wear colored underwear during the clean days on the problematic days. You should not insert a tampon since, according to some opinions, anything inserted internally during the clean days must be examined.
However, a bedikah on day 7 is critical. If you consistently experience staining on the seventh day, this may be problematic. Our first suggestion is to shower normally on day 7 (not specifically cleaning yourself out, just cleaning externally), wait 15 minutes and then perform your bedikah. Hopefully that should help you get an acceptable bedikah.
If staining is significant and you are concerned that you will not be able to get an acceptable bedikah on day 7, we can offer another, more complex suggestion. It is based on the principle that a valid seven clean days requires a bedikah on the first day and the last day, with no more than five days in between without a bedikah. This means that a woman's clean days are valid if she performed bedikot only on day 1 (first day) and day 7 (last day),since just five days elapsed without a bedikah. By this same principle, a woman's clean days are not valid if she performed bedikot only on days 1 and 8, since six days elapsed in the interim.
Thus, if you do bedikot on day 1 and day 4, you can delay your final bedikah until as late as day 10 and still have a valid seven clean days, since no more than five consecutive days will elapse without a bedikah. We recommend that you do bedikot on days 1 and 4 (or even 5 if you are not staining yet), and then wait until the staining subsides before doing your final bedikah. If the staining subsides within less than five days, you may perform a final bedikah during the day, and go to mikveh that night. However, if more than five days in a row pass without a bedikah, you would need to restart your seven clean days.
Here are a few examples: You could do bedikot on days 1, 4, and 10, or days 1,4,5, and 11. If you are reasonably confident that staining has ended earlier, you can of course do the final bedikah earlier (e.g., 1, 4, and 8). You would go to mikveh the night after performing the final bedikah.
We realize this is a complicated suggestion, so please feel free to get back to us with any further questions.