A 16" frame would be the ideal size for you. I'm 5'10 & 18" frame is good for me, though I prefer 17" on some bikes. If you bought it from a local bike shop (LBS) go back & see if you can swap it out for a 16". If you haven't taken it out on any trails yet or at least give it a good cleaning if you have, they might take it back. If you ordered it online, same thing but try shipping it back.