If your flow if really heavy, you will probably leak. One key thing to do is not to pay attention to how the box tells you to put the tampon in. The way I do it is sit on the toilet spread my legs apart, and insert the tampon. You have to lean your back against the back of the toilet. But if you prefer to stand, you can also just stand directly over the toilet, or in the shower. Just remember to try not to sleep with the tampons in overnight. I've done it so many times, but after awhile, I did get toxic shock syndrome, and believe me, it's nothing nice! Also, alternate between your tampons and pads, just so you don't get sick. Another point of advice to you is that it's best not wear your tampons throughout your entire period EVERY month, due to the toxic shock. Also, towards the end of your period, you may not want to use a tampon, and put a pad on instead, due to your vagina being drier than it was during the earlier part of your period. Sometimes it hurts when you pull the tampon out. I hope this helps. Good luck!