Am I overthinking

Ok so me and my best friend and my boyfriend are having a threesome tomorrow and I think I’m overthinking cause he keeps saying he’s going to sleep and then I text and he texts me back immediately. And she’s not responded in a while. Am I just overthinking that they’re up sending nudes to each other? I keep telling him I’m nervous cause I’m scared he’ll like her better than me and he just says that he won’t. Am I just overthinking or do I have to be worried