Help..?

So this weekend was my birthday & I got super fucked up at a hotel with a few friends and my boyfriend, and long story short, I kissed one of the girls that told me she has feeling for me & I don't know why but I kissed her... I'm not into her like that. I really do love my boyfriend & I hate myself for what I did. As soon as I started to sober up that night I told him, and he told me he was just glad I told him right away and that was ok... But it doesn't feel ok... Should I let it go like he is or what should I do? I feel like I don't deserve him...