No kids for me

I've always known I wasn't going to have children. But now that I'm in my mid-twenties with a long term SO (who also doesn't want kids) the pressure from my family and peers is really on. I'm great with kids so nobody understands my choice or takes it seriously. Everyone keeps saying I'll change my mind soon - even my GYN when I asked her about sterilization options. This whole ordeal is making me feel isolated and like there is something wrong with me as a woman.