There wasn't a "middle class" and that is a modern idea. In the middle ages you were one of three types of people. The church, noble, or serf/peasant. A middle class won't develop until the...
The lines distinguishing one class from another are quite blurry these days. It would be fair to say, however, that it used to be middle classes were all professionals with university degrees...
In the middle ages the king was obviously at the top and the peasants at the bottom so the "Upper Middle Class" would have been comprised of nobles because the nobles were ranked amongst themselves...
middle class means someone who has the means of production in a economy, while working class is someone who takes home a wage/salary. So unless you own a business that employs people outside your own...