What Size of American Apparel Fleece Flex Hoodie Should I Get?

I want to buy an American Apparel hoodie in mermaid green. I'm a 14 year old girl. im about 5 ft 5 in. i weigh about 109 lbs and wear a 36A. I dont want the jacket to fit tight, i want it kind of baggy. WHAT SIZE SHOULD I GET? I wear medium shirts at aeropostale and hollister. i wear large jackets from those stores as well. they all seem to fit me perfect, (hope that info helped).