My trailer moves around a bit, my wife and family are also heavy walkers. I put the small adjustable screw jacks someone posted a few pages ago under mine, three per side in addition to the four factory feet. Makes a huge difference!! Far more I have found then just adding let's say the xchocks.
We're seasonal so it's not a huge deal for me, if I was traveling I would probably just put one or two around the door and on the opposite side. Lots of folks here have them on cinder blocks or rail ties.
Every trailer I have ever had has moved around with people inside, but never enough that I couldn't "take care of business."
As mentioned it's possible you didn't have enough weight on the jacks. It's always a good idea after setup to go around and check them, I have found they often need adjusting after setup. Another thing that was also mentioned was don't extend them all the way, I typically have 4-5 flat leveling blocks under my extendable jacks.