Missing and hard cranks

My 2001 Alero sometimes starts really rough at start up, and I've had my brakes change several times and they always squeal and make a sound like there is no pad on it. Also there is a gas smell coming from under the hood I think it may have something to do with the fuel injectors and sometimes when driving the car sometimes misfires, not some loud popping noise, it will jerk while I'm driving mainly at high speeds on the freeway