Mazal tov on your recent marriage!
We generally advise women not to look at toilet paper and to wear colored underwear (not necessarily black) when not expecting to be niddah, so that they do not find stains that would render them niddah unnecessarily. This recommendation is based on the assumption that there is no reason for a woman to be getting her period at these times. At times when a woman does expect to bleed, such as yemei perishah, she certainly should be aware of what is going on. Therefore, a bedikah is required on a yom perishah. If her yom perishah passes uneventfully and she is still expecting her period, she should be extra careful to be sure she is not niddah before having relations with her husband.
One way to avoid doubt would be to check for bleeding in a way that will not cause you to become halachically niddah. If you wipe yourself externally with toilet paper without urinating (or at least a few seconds–ideally 15 seconds–after urinating), you can tell if you are currently staining. If you find a stain, we recommend refraining from relations for about 24 hours to see if the staining continues, but that stain does not make you niddah. You can continue with other physical affection, and after 24 hours if you find out the stain was a fluke, you can resume having relations as well. If the toilet paper is clean, you can have relations with your husband without being concerned that you might be niddah. (Note that this recommendation works according to many authorities, including the posek for this website. However, some halachic authorities rule stringently regarding toilet paper even if it does not immediately follow urination.)
Another way to remain aware of your situation is to wear colored underwear that is not black. A stain found on underwear of any color but white or off-white does not make you niddah, but will help you be confident that you know your situation. When finding a stain on colored underwear we suggest abstaining for 24 hours without assuming you are niddah, just as with finding a stain on toilet paper.
Beginning to keep hilchot niddah is not simple for most newlyweds, and time and experience do help you gain confidence that you know what you are doing. Until then, feel free to continue asking questions, and keep in mind that as a married woman you are meant to have relations with your husband (it is no less of a mitzvah than being strict about hilchot niddah!) and that as long as you are careful at times you are meant to be, such as yemei perishah, you need not be nervous at all times that you might suddenly be staining for no reason. If you are nervous nonetheless, or are experiencing cramping which might be related to your period, you may take the precautions described above of wearing colored underwear and looking at toilet paper not after urinating.
Thank you for your compliments, we are so happy to be of assistance, and we will pass them on to the hotline staff.
This response has been updated to reflect the rulings of our current Rabbinic Supervisor, Rav Kenneth Auman, regarding waiting before wiping.