I'm 19yrs old and have bone pain in my back and legs. Never at the same time but my leg bone pain is getting bad. What could it be?

It could be bone or. It is often hard to separate muscle pain from bone pain. Unless you have done unusual or excessive walking or running, it is hard to pin point what is going on. You should try resting for a few days and use mild pain medicine like tylenol (acetaminophen) couple of times a day. If it did not settle down in 3-5 days, you should go see your doctor and ask him to check you to find out why you ahve these pains.