Could a childless 18-year-old get an IUD/IUC?

A year from now, when I graduate from college, I'll be losing my parent's health insurance, which means that I'll start having to pay out of pocket for my birth control (currently NuvaRing). I will be 18. My serious boyfriend and I do not want children, and he is actually pushing for a vasectomy as soon as he turns 21, which is in just a few months. I don't like the idea of us doing something that permanent right now, but in the mean time we, of course, don't want to get pregnant. I know that doctors don't normally like to put IUDs such as Mirena in women who haven't had children yet, but because of our career paths I know that there is no way he and I would even /consider/ having children for at least another 5-10 years and it sounds like the best option for us. Why don't doctors like putting them in childless women and do they often make exceptions for people like us?