My lower back down to my tail bone are sore almost evetyday. i have fallen pretty bad a few times which may have made it worse. what to do?

Get an X ray: Since you have injured or fallen few times and its hurting you i suggest you get an x-rays at least. Start to take aleve (naproxen) twice a day. Most common is soft tissue damage at your age 18, but you may have other underlying pathology which needs to be resolved or ruled out. If you ignore yourself at this age you may pay the price later.