The Wal-Mart Waddle

During my first pregnancy I took a birth prep class with a teacher who also taught prenatal yoga. She said that if you don't work out and keep you back muscles strong you will develop (what she dubbed) the the Wal-Mart waddle.
Because of her I now obsessively try not to look like the lazy, back-holding, feet-dragging, ducky mom who also happens to shop at Wal-Mart.
It is almost impossible.
My back has that curve. I either waddle or slump and they are both very odd and uncomfortable so I'm attempting to do something about this.
As often as I can, I lift weights making my arms and legs stronger and I even do some questionable moves to strengthen my back. Questionable because I'm not sure that I can keep this up and I'm not sure I'm not injuring my back by doing what would be safe and normal for a non-preggy.
I also purchased some preggy workout videos. They were around one dollar before shipping so they are pretty old. One is with Denise Austin and her peppiness is...well...nauseatingly uplifting. Plus Bella comes in while I'm working out and wants to dance with me to the music while holding my hand. Who can say no to that?
Last time I was pregnant I took a prenatal Pilate's class and I liked it until one of the other mothers was doing a very simple crunch move while holding on to her legs, the poor girl tooted so loudly that I was hysterical with laughter for hours and very aware that could happen to me. I refuse to go to a class where this could happen because my embarrassment factor is ridiculous. Overly paranoid? Probably.
Last time I gained 40 lbs. Also ridiculous. I cannot, will not, should not do that again.
I guess Denise and I will be getting to annoy each other better.