Track and field help?

Tomorrow is the high school track meet and I'm a little bit nervous because i feel like i'm going to be the slowest person. I'm doing the high hurdles and the 4x1 relay. I haven't tried doing all 10 hurdles yet but I've been practicing on 3, i also get a lot of air time. Will I be a lot slower than the other runners? Would i need to slow down to conserve my energy? Also, my PR for 100m is 16.7, but thats without the hurdles.