Hey, boytoy. You're not crazy in the least. I can totally totally imagine having that conversation with my lovers. Insecurity is the rule rather then the exception when a new person joins an established couple and to have it manifest as anxiety is very normal. It will almost certainly get better with time and there are resources to help you work on it (www.morethantwo.com
is a good place to start).
My girlfriend and her husband and I aren't having sex right now so I refuse to put myself in a situation where I'd end up crashing at their place. Between the lack of physical intimacy and the fact that I'd be sleeping on the couch rather than in their bed because they're co-sleeping with their new baby, I just know I'd be an emotional wreck by the morning.
I think it'd be really helpful for us to have some context. How did you guys get together, how did you end up living together, what types of sex do you have or not have?
It's going to be ok, little guy, it really is.
If they love you they'll listen if you tell them that you're having a hard time. Then the three of you can work together to come up with a better sound proofing system then a towel until this gets easier for you. I'm sure they want you to be comfortable and happy, right?