Ftm packing and harness?

Ok, so I'm 16 and new to packing. I want to see if it feels right because lately I have been having a lot of dysphoria. I made the gel and condom packer but I don't know how to keep it from falling out of my boxer briefs. Is there a way to make a harness (can't really buy one)? Also any other ideas for making packers that are a little more durable?