How can a plus size woman dress for a formal dinner?

I have recently gained a lot of weight. I went from a comfortable size 16 to a size 20. I have been down from a knee injury, and because of that, I haven't been able to move around and exercise. My problem is, my husband has been invited to this gala dinner with his job. Now that I have gained this extra weight, I don't know how to dress for this,being a plus size woman now. He tell me all the time, I still look great, but I am so self conscious with myself now. Along with the weight gain, I have developed a big stomach as well. I look as if I am pregnant now. My question is, how can I dress for this event and still look great. Please, no harsh comments, as I feel bad enough already.