Just because a yarn is worsted weight does not necessarily mean it will be heavy. You can find some ribbon or tape yarn that is classified as worsted weight but is relatively light.
Cotton tends to be heavy relative to other fibers so if you find a worsted weight cotton blend the yarn will be lighter.
However, if you prefer the look of garments made with finer yarns there are lots of patterns out there. Don't worry whether or not a pattern is "easy" but select something you would like to make that you think would look good on you -- it will become incentive to learn techniques.
Check out the free Shapely T at [
www.whiteliesdesigns.com] or the various patterns at [
www.knittingpatterncentral.com] or the Lion Brand or Bernat websites.
If you don't find a free pattern you like, check out what's available at your library either at your local branch or through inter-library loan.