Am i getting too jealous or is there something i should be worrying about?

Okay. I sometimes get jealous when my girlfriend hangs out with other guys because of the whole protective thing. But recently, my girlfriend has been hanging out with 2 of her guy friends, her and the two of them. Now, both of them are geeks, and seemingly unattractive, but it still makes me wonder if shes doing something behind my back. One reason is that one of her friends she was hanging out with was boasting he could last an hour and a half about sex, and she told me she was walking past him when she heard it and she said 2 hours. She said that her guy friend said that hes jealous of how long i can last, since she mentioned 2 hours to him reffering to us. It makes me wonder if she said that because she wants to instigate something to him or what? Another reason im suspiscious is because she leaves for like 6 hours with 2 of her guy friends. Like today, she was talking to me on facebook, and i was mad because she hadnt responded to my texts in like 5 hours, yet she was on facebook on her phone. I asked her what she was doing, and at 10:30 at night, she was apparently on her phone listening to music while sitting on a slide in a park with two of her guy friends. I asked her why and how she finds it fun, and she said that just talking to her guy friends is fun. Maybe im worrying too much, but i dont see how you need to meet up with 2 guy friends in a park at night just to talk and listen to music. I told her if she wants to talk to them she can do it over a phone. Anyway, i asked her if she does anything with her guy friends she isnt suppose to, and shje says no, and i belive her. But maybe im worrying too much, but i just dont find it okay how she goes to parks with her firends just to talk. Should i question her again?