Dear bridesmaid dress retailers and manufacturers

Monica • My husband and I are 36 and 35, high school sweethearts, married in 2005, son Gavin born 11-27-15. PSU grad, work for small newspaper as a reporter.
The average woman is not a size 4. And why do the dresses run small? Nothing knocks your self-esteem down a few pegs like not being able to try on any dresses because the sample sizes are too small. Even the 14 was too small, and my usual size is 12. Meanwhile, my six months pregnant sister was practically swimming in a size 6. So frustrating.