Fear of sleeping over at someone's house?

When I was younger (around eleven or twelve), my little sister developed a Separation Anxiety Disorder. She was terrified to sleep away from home, and convinced that if she did something really bad would happen, like our parents dying or something. Eventually she grew out of it, but not before her panic had infected me. It started out as SAD, but eventually I lost the fear that something bad would happen, and I'm just terrified of sleeping at a friend's house. I'm fine sleeping at family member's houses, and I'm also fine camping or staying at hotel's...but the thought of spending the night at even my best friend's house makes me break out in a sweat. I've had this issue for years, I'll be Seventeen in November and I haven't spent a night at someone's house since I was maybe twelve. I'm pretty sure this is agoraphobia (not the fear of going outside. that's not what agoraphobia is. in case you were confused :P). I'm just wondering what this might be called. thanks :)