This is a great question. In order to answer it, let's think about the differences between living on Earth, and living in space.

On Earth, we are surrounded by an atmosphere made up of gases, which is what we breathe. These gases push on our bodies. Space is like a vacuum. There is almost no gas in space to push on our bodies. Our bodies may expand a bit, because of the lack of pressure, but our skin would keep our bodies from exploding, like a sandwich bag.

One way to understand the difference between being on Earth, and in space is to collect a bunch of pillows, lie down and stack them all on top of you. As you stack more pillows, they push on your body harder. The pillows are putting pressure on you, like the gases in Earth's atmosphere. Now kick all the pillows off. That is how it would feel in space, no pressure.