Hi Khris - wow, 30 dresses! I would probably have given up half way, trying on clothes is such an effort sometimes! I don't know if you have an H&M store where you live, but I found these two - pure cotton, good bra coverage and sizes up to 16. I don't know about the length, though - the dresses are about 35 inches long, so it depends on how tall you are. From what I've seen, your body shape is similar to mine, and I find that H&M dresses fit me quite well.
Dress no 1 comes in khaki, light coral, dark lavender and black in addition to the raspberry red in the picture. Dress no 2 is also available in a dusky rose colour and taupe.
I don't know if this is any help at all, but I wish you good luck on finding your perfect summer dresses!