Summarize:

Sometimes, overflow happens. In fact, it's happened to most at one time or another. If you bleed through onto your sheets at night, rinse the sheets in cold water and then immediately put them into the wash. If you bleed into your underwear, you can try washing them (separately or with dark colors), or just throw them away at the end of the day. Worst case scenario is that you bleed into your pants or skirt do what you can to get through the day by tying a sweater around your waist or, if you must, going home early. Shower, change, and move on with your day stress-free. Talk about your accident with someone you trust. Remember that 50% of the world has dealt with periods it's likely that someone you know has had an overflow accident, too. Don't be ashamed or embarrassed to talk about it and how you feel. If you've experienced overflow bleeding, be prepared for next time. When you're on your period, wear black underwear and pants. If you do have some spotting, it won't be noticeable. You can even set aside a set of dark undies to wear only when you're on your period. Using more than one type of menstrual hygiene product can be really effective in minimizing overflow bleeding. If you sometimes bleed through your tampons, use a panty liner or pad, too. That way you have some backup in case you don't get to change your tampon in time. THINX period panties can also be a good backup method to a cup or tampon. THINX are made so that you can bleed right into them, then wash them out and reuse them. They hold anywhere from to 2 or 3 tampons worth of blood depending on the style, and are available to purchase online. Get used to "checking on things" every hour or two. Make a quick bathroom stop in between classes or as a short work break. Check your underwear and pad, and do a wipe test if you're using a tampon if there's blood on the toilet tissue after you urinate, you may be about to bleed through your tampon. Put a dark towel down on your sheets while you sleep to protect your bedding and mattress from accidental leaking. You can also try using overnight pads that have wings; these offer more protection from spillage.
Stay calm if you overflow. Wear dark clothes and underwear while on your period. Double up on your hygiene products. Be vigilant. Protect your bedding with towels.