How do i know how serious my ankle injury is? i twisted my ankle walking (rolled it) and it hurts pretty bad and is swollen. could i have broken it? if it is a sprain, do i need to see a doctor or will it just heal on its own?

You : You certainly could have broken it, and most broken ankles are from a simple "inversion injury." doctors use a set of rules known as the ottawa criteria to decide whether or not a sprained ankle or foot needs an xray. You can do a quick search for "ottawa rules" on the internet and see what they involve, but the bottom line is that the interpretation of the rules requires a bit of knowledge of anatomy, so they can be a bit difficult for a layperson to interpret. Basically, i would recommend seeing a doctor unless you have no trouble walking and the only spot on your ankle/foot that is tender and swollen is just below and in front of the lateral malleolus (the bony lump on the outside of your ankle). Even if is just sprained, it may still be beneficial to see a doctor to get a supportive boot known as an "aircast.".

See a doctor: A bad sprain can take longer than a break to heal. I would see a podiatrist and get an x-ray as well as an evaluation of the ligaments.