I feel ya hun. I went from having a whole bunch of friends to having a small handful just because we're at different places in our lives now. I don't need to be around party people and the party people don't need to be around a baby. It helps to remember that when they start having kids they'll likely call me up so they can have a mom friend, just try not to hold it against them. Everyone has different priorities, you know?
I was the first of my friends to have a baby at 19, it seems once everyone hits there twenties , well, some have babies. I have 5 friends that have kids now. You could always join a mommy group and befriend some moms of all ages. :)