The universe is gradually expanding over time, growing larger and larger with each passing moment. You may have noticed that your own body is expanding, too. This is not a coincidence. When your body expands, acquiring additional volume and mass, it’s because of a basic, inescapable physical phenomenon.
Don’t blame yourself—or blame anything else. What’s happening to you is a natural process, as Cyanide & Happiness explains.
-via Pleated Jeans
Space between galaxies does expand, but not between the atoms of your body, the atoms interaction is way too strong for that to happen.
Here's a very well made video on the subject:
https://www.youtube.com/watch?v=th_9ZR2I0_w