Wear anything you have that fits. Clothes that are too tight, oddly enough, make someone look fatter and clothes that are too loose make someone look ill, huge or silly. A good fit makes you look the size you are. If you can, during the pregnancy, eat as healthily as possible, and maybe you won't gain a lot (meaning, maybe some of the baby weight from your last pregnancy will go down).
You should wear whatever makes you comfortable. Think about how you feel and make yourself pretty for you you. Who cares what others say or feel. This is your time. Be a happy momma!! Congratulations!