M.L.
I am 5'5" and 135 and wear a 6. At 130 I wear a 4. I work out a lot and have an athletic mesomorph build. I would say I'm a very average build - not "man-ish" and not "waifish." When I was younger and not as strong I wore the same sizes and weighed 115-125. But I wasn't as hot. LOL (That's old people humor.)