Post menstrual spotting

Not all spotting invalidates the clean days.  For example, stains on underwear or another external surface that are smaller in size than a gris (roughly, the size of an American dime or Israeli shekel) do not invalidate the clean days. Changing underwear frequently can help you avoid allowing stains to reach this size. Other stains may be acceptable based on their color.

Bright red stains on a bedikah are problematic whatever their size, but some other colors are acceptable, and even the hefsek taharah need not be completely clear.

As a rule of thumb, light tan or yellow stains with no hint of a reddish tint are generally acceptable.  Other browns depend on a proper evaluation.

In other words, your first step is to bring cloths or stains in to a rav for evaluation, rather than assuming you must delay or cut short your clean days.  You should also explain to the rav your difficulty in getting to mikveh on time; he may advise you to reduce the number of bedikot.

Some women find that a douche (doctor permitting) or a long soak in a tub before the hefsek taharah helps reduce spotting that would otherwise delay the clean days.  Natural remedies are unreliable (and unregulated), but we have heard anecdotal reports of success with drinking shepherd's purse tea from the first day of bleeding.  It would be best to consult with a practitioner of natural remedies for further advice. (Note that shepherd's purse is a powerful herb. It may not be used during pregnancy, and its use while breastfeeding is debated – a breastfeeding mother should not try it without the guidance of a qualified professional.) Medical hormonal remedies could also be explored with a physician.