What should you do when you find out you 2 of your best friends have been talking about you behind your back?

This can be a difficult situation but the best way is to confront them. When you confront them, it's important not to get angry. Although you may be hurt, anger isn't going to solve anything, just lead to more conflict. Calmly approach them during a time when you can both talk alone. Tell then that you have heard that they have been talking about you behind your back. If they apologize, try to forgive them. This may be a hard thing to do and it may take a long time, but holding a grudge will only build up more anger inside of you. If they try to lie, or don't take you seriously, you might want to consider finding new friends. Especially if this isn't the first time. Friends who constantly talk about you behind your back or lie to you are not true friends. Good luck!