quilting cottons and dress weights are lighter fabrics than is used in most bedding. You want a broad cloth or a medium weight linen. Linen is wonderful for bedding, it is very sturdy and only gets better with age and use. Also think about looking for those iconic white damask table cloths found at most all thrift shops. The weight is right and can be dyed for great effect. Soft on the skin and mostly all cotton unlike modern sheets and pillowcases. The price is right as well. Fabric.com and the fabrics-store.com
http://www.fabrics-store.com/blog/2012/02/16/1300/ offer good deals. I have shopped both for linen and have never been disappointed. Lastly consider when shirting fabrics go on sale as they do frequently on fabric.com. They have a lighter silkier feel but are very sturdy as shirts get a lot of wear, you get some nice plaids and stripes, they are usually much wider than 45" and make great pillow cases.