You are definitely facing a number of challenges, and these questions only begin to touch on them. Our hearts go out to you, and we are here to assist you in any way possible.

You are correct that there is no way for you to bring the cloth to a halachic authority for evaluation right now.

We recommend that you call the halachic authority to whom you usually bring such questions to consult. (You could also contact a Yoetzet Halacha through Nishmat’s Golda Koschitzky hotline, or a local Yoetzet Halacha.) Explain that you cannot bring in the cloth because you are in quarantine, and give as many details about it as possible. Depending on your description, they may tell you that it is permissible.

Another possibility is to seek to have it evaluated by a rabbi online through the Tahor App (available on iPhone and some models of Android phones), which uses special color calibration technology to ensure that the stain is photographed and transmitted accurately.

In this situation, you might try to perform another bedikah prior to sunset, to serve as a new hefsek taharah should one be necessary.

Please note that if your seven clean days finish before you exit quarantine, you will need to wait until you finish quarantine before immersing. You should complete the clean days on time as usual, even if you will need to delay immersion. After counting the clean days, you need not perform any more bedikot, and you should switch to colored undergarments.