Formal black tie dress

Ri

I'm needing a formal black tie dress preferably black for a black tie wedding. I'm going to be 7 months pregnant. I've had multiple pregnancies and I'm huge this time so worried in a few months how big I will be. I've asked for help before but the responses were both expensive and not black tie appropriate. Help a plus size mama out I'm desperate to find a dress. 3xl size 24 normally.