OK, First of all, if you're blowing 20-Amp fuses, you have a serious short somewhere that needs to be removed. ASAP! Check this link to read up on towing connectors and how they are wired; https://axleaddict.com/rvs/RV-Towing-and-Electrica...
Then, unhitch your trailer and check out the wiring in your Rv to the tow connector. With such a short, you could have some melted wiring insulation that will haunt you in the future.
Once you're confident that the RV wiring is still good, then you should check that your trailer wiring doesn't have a short in it.
I would look at this from a different perspective than others. A 2005 motorhome has traveled a lot of miles without having those fuses blown. Because of that, I would suspect one of two things; 1-someone has been messing with your internal RV wiring, or 2-the trailer you are trying to hook up is not wired properly.