well, I guess the obvious place to start would be to look at the sticker on your trailer hitch receiver on the back of the motorhome. What does it say regarding tongue weight limits and weight distribution?
after that, what is your tongue weight?
Now you'll have the info you need.
From here on I'm just guessing, but usually anything over 500 pounds tongue weight needs a weight distribution hitch. And a 5500 pound trailer 'should' have a tongue weight of around 660 pounds. Maybe more, hopefully not much less. So my guess is yes, you need a weight distributing hitch.