What do you want to cover up, accentuate, etc?
Yes a maxi dress can be dressy enough! I've found tulip and peplum styles are really flattering on my post pregnancy shape. Maybe have a look at those styles? You need to go shopping and figure out what suits your new shape- it honestly took me months to figure this out after I developed womanly bumps everywhere
Afraid to say you may never love it again as it isn't 'your' shape. I struggled with body issues after Ella and wore maxi dresses to hide in. I have only just got the confidence to wear dresses that accentuate things again now and I guess it's because I've come to terms with the fact that I will never be a size 8 with a boys figure again! Give it a few more weeks, go shopping (ideally with a girlfriend that will be completely honest with you, I used my younger sister and she was brilliant) and try lots of styles on xx