@BitsHead am I correct if I guess your DH is a bit older than you? I remembered from a previous thread (sorry your name just sticks in my head!) that you're 20 but he has much older kids? Like almost close to your age??
I'm wondering whether now you've had the baby and have snapped back to your pre-pregnant self he's feeling a bit threatened? I may be way off base but I could see how that might happen with a large age difference. He suddenly feels old and you dressing like a normal 20 year old emphasises that.
I'm not excusing his behaviour and honestly when you say he liked to show you off I internally cringed. You're not a dog at a show. You're a human and the mother of his child.
He needs to either grow up and accept you dress the way you dress (which o guess hasn't changed since he first met you) or deal with his feelings in a mature way.