Plus sizes are reserved for women who wear size 12 and higher. It may be that they are large in height, weight or waist.
Unfortunately, our society seems to be obsessed with thin women. American culture did not used to be that way. Cosmetic companies found a gold mine in inducing women to look slim, specially young girls and professional women. If you looked at other culture, large women are not self conscious and go about their duties very efficiently and without being insecure.
So what to do? My advice first and foremost is, if you are truly overweight and doing everything reasonably possible to address it, stop worrying. Worry increases your bad cholesterol, causes anxiety lines and raises your blood pressure. All of which in turn increases your water retention and weight, since it impairs your metabolism. So be confident in yourself, and stop thinking of how others think of you. You have no control over that.
Second, dress appropriately, keeping in mind the lines, colors and contours of the dresses you wear and your figure. I highly advise utilizing services of a dress expert, particularly if you are in a professional field.
Third, simple colors, contrasted intelligently, will give your figure a lift and make you look snazzy. Here is one—a white skirt, no lace or frills, and a charcoal grey top, with a maroon scarf. This sets you apart. White is always a choice color for large women. Red, except as an accessory (a purse, bracelet or a scarf) is a no-no. So however tempted you are after looking at the beany figure in the magazine, do not go for it. Red sharpens lines, so if you are a bit heavy in the hip, it will spell you FAT or VERY FAT. Stay away from gaudy stripes they also accentuate your figure. Sometimes you can improve your look with a snappy brooch.
Next, make up and hair. Again, stay away from extreme colors like red, maroon, green etc. Tan or opaque colors and lighter shades will dampen your extra large figure and accentuate symmetry which is what you want. This is true whether wearing lipstick or dress. About hair. Bleach only if you must. Bombshell blonds or silvery sirens have to have a waist of 26, not 36! Best hairstyle is one that sits closer to your face, not one that flares out. No ponytails, but your best friend could be a distinguished looking hair clip, and hair framed around it.
Shoes? I am constantly amazed how many tall women think they need 4 inch stilettos! Again, no red, black or dark tan colors are good. Sandals with large flowers—-absolutely not! If you have to, you can go with some sequins as well.
Now the emotional part. Are you happy with your life. If not, go change what you can first, before worrying about how you look. Believe me, inner confidence exudes outward. When you meet and greet people, look them in the high and use a semi firm handshake. Be one of the crowd and they will adopt you like an old friend.