Opposite Gender Friends

Prior to my committed relationship, I used to predominantly hang out with male friends whom I thought genuinely liked me for my personality. (I admittedly have a boy's humor and have a thing for video games, guns, the wilderness, and sports.) Upon finding out that I now have a boyfriend, most of them have pulled away to the point that I no longer have my stable group of "friends" to hang out with. My SO doesn't have the problem of losing his guy friends, but many times when he introduces me to a female friend of his, they also start acting strange and stop interacting with him altogether. How does one -- if possible -- maintain healthy, platonic friendships with the opposite gender when in a loving, committed relationship? Or should these supposed friends just be left in the past?