I screwed up

I don't really have an interest in going to prom but now that the prom is this Saturday and all my friends are going I feel left out and that I'm missing out but I just really didnt see the point in spending all that money for one night, I start school in the summer and I'm moving by myself to another state. I feel bad for not going because my mom really wanted me to go but I just really didn't want to but now I do and I feel crappy. It's my own fault, I know but I just felt like venting because I always feel like ive let myself down in some way