What is the trailer made out of? Make/model? I'll need to know what you have and what its capabilities are before I can make recommendations on how. The above poster gave useful information. I plan to build a camper trailer towable by bicycle, but have not started yet.
Post pics if you can. In all likelihood you probably won't be able to build anything extravagant out of it, but depending upon what it is, perhaps you might. Aluminum fatigues over time and this trailer was designed with a specified weight limit in mind.