Help Im confused and sad and frustrated...?

Ok well i had this crush for 2 yrs on this guy but when i really start getting close to him this year he ends up dating my best friend. So i thought maybe in a couple of weeks they will break up but no they are still dating for 4 months and now this week i got so close that i went to his house with my two friends (girls) and i was flirting with out knowing it and then i thought he was acting weird and my friend told me i was flirting and he knew so he was avoiding me while i was there. When i left i felt so guilty and then i started texting him today and i had a feeling that he was trying to show that he loves my best friend and i felt like a stalker. I know that she likes him but not loves him. I just want to get over likeing him. So... can you help me?