help?

i'm asking in the random section because not many people go to the advice section on here. anyway, ive liked this guy for 3 years and my feelings for him are really strong. recently i found out that he's liked me back the whole time, but now he also likes my ex-best friend and asked her to formal last week (she said yes). so he likes both of us now but he likes my old friend (R) more because shes less moody than me, and me and my ex-bff have been on civil terms for awhile, but i dont know what to do from here. me and the boy (L) talk constantly but he also talks to R a lot too. what if R likes L back (we dont know if she does)? it makes me a little mad because i used to always talk about how much i liked L to R, and now shes backstabbing me and going to formal with him. help? i dont know what to do, or how to approach R to talk to her about it.