Do. Not. Attend. Prom. With. Someone. Who. Makes. You. Miserable. I shouldn't have to say more, but I'm not good at the tough-love, so I'll give it to you softly. It just doesn't make any sense to break your neck struggling to find a date, any date, just to end up having a crappy time with a jerky loser who looks like Bigfoot.
If your ex is still a close friend who treats you well, then go ahead and go! But don't do it to get back at someone or piss off a jealous friend. Do it because you've chosen the person you sincerely want to spend the evening with. You are not obligated to attend prom with anyone.