I had sex by accidence with a girl and now I feel violated?

I'm 14 and yesterday was my first experience of sexual intercourse with my bestfriend. Right, first of all I fancy my bestfriend, her name is Anna and she's rather beautiful, she's 16. It all started yesterday, when we were talking about truth and we both agreed to share our most deepest secret. Mine was something unrelated to her. She was the first to go, so she told me that she has a huge crush on me. I was shocked, our faces were both red! So i'd figure to kiss her to express my feelings about her too. Well that kiss became intense and it leads to sex. I know i should have stopped her before it happen, but when i looked at her she was so excited and happy. I just can't do it, i don't have a heart to say it, all i can do is just go along with it. When we woke up, it was VERY AWKWARD! We knew each other since we were 10! What's the protocol, what should i do now??